user-1: I once found a program that was capable of creating Bitcoin addresses with specific words in them, but can't find it now.  Is there a trusted program, in the Ubuntu repositories for example, that can generate these 'vanity' addresses?

user27170: You can use something like VANITYGEN.


Vanitygen is a command-line vanity bitcoin address generator.

If you're tired of the random, cryptic addresses generated by regular
  bitcoin clients, you can use vanitygen to create a more personalized
  address. Add unique flair when you tell people to send bitcoins to
  1stDownqyMHHqnDPRSfiZ5GXJ8Gk9dbjO. Alternatively, vanitygen can be
  used to generate random addresses offline.
Vanitygen accepts as input a pattern, or list of patterns to search
  for, and produces a list of addresses and private keys. Vanitygen's
  search is probabilistic, and the amount of time required to find a
  given pattern depends on how complex the pattern is, the speed of your
  computer, and whether you get lucky.
The example below illustrates a session of vanitygen. It is typical,
  and takes about 10 sec to finish, using a Core 2 Duo E6600 CPU on
  x86-64 Linux:
$ ./vanitygen 1Boat Difficulty: 4476342 Pattern: 1Boat
  Address: 1BoatSLRHtKNngkdXEeobR76b53LETtpyT Privkey:
  5J4XJRyLVgzbXEgh8VNi4qovLzxRftzMd8a18KkdXv4EqAwX3tS Vanitygen includes
  components to perform address searching on your CPU (vanitygen) and
  your OpenCL-compatible GPU (oclvanitygen). Both can be built from
  source, and both are included in the Windows binary package. Also
  included is oclvanityminer, the vanity address mining client.
  Oclvanityminer can be used to automatically claim bounties on sites
  such as ThePiachu's Vanity Pool.
Current version: 0.22
Windows x86+x64 binaries here. PGP signature here.
Get the source from GitHub. Includes Makefiles for Linux and Mac OS X.
Main discussion at BitCoinTalk
The latest source doesn't work properly for high-end AMD cards (7XXX
  and greater). Solution is to change line 459 in oclengine.c from:
  return quirks; to: return quirks & ~VG_OCL_AMD_BFI_INT; Windows
  x86+x64 binaries that solve this problem plus provide support for
  compressed keys here. PGP signature here. If you have any problems
  with the binaries, join the relevant BitCoinTalk discussion.

Proper syntax for VanityGen is:
Usage: vanitygen [-vqrikNT] [-t <threads>] [-f <filename>|-] [<pattern>...]
Generates a bitcoin receiving address matching <pattern>, and outputs the
address and associated private key.  The private key may be stored in a safe
location or imported into a bitcoin client to spend any balance received on
the address.
By default, <pattern> is interpreted as an exact prefix.

Options:
-v            Verbose output
-q            Quiet output
-r            Use regular expression match instead of prefix
              (Feasibility of expression is not checked)
-i            Case-insensitive prefix search
-k            Keep pattern and continue search after finding a match
-N            Generate namecoin address
-T            Generate bitcoin testnet address
-X <version>  Generate address with the given version
-t <threads>  Set number of worker threads (Default: number of CPUs)
-f <file>     File containing list of patterns, one per line
              (Use "-" as the file name for stdin)
-o <file>     Write pattern matches to <file>
-s <file>     Seed random number generator from <file>

The important options to know are -i and -r which cause the search to be case-insensitive and use regex, repsectively. In its simplest format, you issue a command like:
vanitygen.exe 1david
Which tells vanity gen to look for an address with the exact prefix "1david." On a single core of my core i5 this runs at about 325,000 keys per second as shown by the status display (which does show a time estimation.):
[324.43 Kkey/s][total 15166208][Prob 0.1%][50% in 9.1h]

Using the -i option drastically decreases generation time. vanitygen.exe -i 1david produced the following results in just a few seconds:
Difficulty: 36384905
Pattern: 1david
Address: 1DAVid3iW7XhDBzdoj8FbnaSaqWCjeTgUP
Privkey: 5JvtXtpUbwbNNqRoQjF3w2nyXHhphJk6LX1pWkPYEkBr4nnnBeL

The -r option allows the specification of a regex value instead of the default pattern option. If, for example, I demanded that my address contain all lowercase letters but I don't care if the "D" in "David" is uppercase or not, I could use vanitygen.exe -r 1[Dd]avid. One downside to specifying a regex prefix is that you will not be given any estimated time or probability data since such calculations are not as trivial as matching a simple prefix.
The more specific your matching criteria (and the longer the pattern) the longer it will take to generate your address(es). This can be sped up considerably if you have an ATI/AMD video card since there is also an OpenCL version of VanityGen which can try millions of keys per second on a decent GPU.

user35507: If you want to create an impressive vanity address, it might be easier to outsource it.
https://vante.me is a service that calculates Bitcoin Vanity Addresses.
As they use split-key address generation, you are sure that you are the only owner of the private key.
More info here:
https://www.reddit.com/r/Bitcoin/comments/4iaifs/vanteme_a_secure_and_convenient_service_for/

user323: You can generate a vanity address using various generators, such as Vanitygen for example. This option assumes you have a computer with decent GPU, as creating a long vanity address requires a lot of computation.
If you don't have a particularly good piece of hardware and would still like to own a lengthy address, recently split-key vanity address mining became a bit popular. You can use online websites, such as my Vanity Pool, to request a vanity address to be mined for you for a fee. If you want to understand how this option is possible and risk-free, you can find the discussion of this problem on the Vanity Pool Bitcoin Talk topic.

user2089: !WARNING! The vanity address site below was hacked in December, 2013, but the site owner only recently posted an update admitting the hack: https://bitcointalk.org/index.php?topic=118968.0
More than 4 Bitcoins total have been stolen to date, as you can see from Blockchain records (note the number of vanity addresses dumping coins, and you'll see that probability alone is proof, supported by all of the users who lost their BTC):  https://blockchain.info/tx/9e95fd443621d3d9fc150f290144401feb1627573c9161beb08edb472069a819
The site owner has taken down the site, but for how long is up in the air. As Stack Exchange keeps long archives, I wanted to make sure this warning stuck here for all to see, but did not want to edit the original response.
You can also use https://bitcoinvanity.appspot.com
All done for you on their website and nothing to install.
Is secure as they never know the private key - see help on site for how this is possible!

user1153: I guess you mean Vanitygen:
https://bitcointalk.org/index.php?topic=25804.0
From that page:

Vanitygen is a command-line vanity bitcoin address generator.
Vanitygen accepts as input a pattern, or list of patterns to search
for, and produces a list of addresses and private keys.  Vanitygen's
search is probabilistic, and the amount of time required to find a
given pattern depends on how complex the pattern is, the speed of your
computer, and whether you get lucky.


-1: <p>I once found a program that was capable of creating Bitcoin addresses with specific words in them, but can't find it now.  Is there a trusted program, in the Ubuntu repositories for example, that can generate these 'vanity' addresses?</p>
 27170: <p>You can use something like VANITYGEN.</p>

<blockquote>
  <blockquote>
    <p>Vanitygen is a command-line vanity bitcoin address generator.</p>
  </blockquote>
  
  <p>If you're tired of the random, cryptic addresses generated by regular
  bitcoin clients, you can use vanitygen to create a more personalized
  address. Add unique flair when you tell people to send bitcoins to
  1stDownqyMHHqnDPRSfiZ5GXJ8Gk9dbjO. Alternatively, vanitygen can be
  used to generate random addresses offline.</p>
  
  <p>Vanitygen accepts as input a pattern, or list of patterns to search
  for, and produces a list of addresses and private keys. Vanitygen's
  search is probabilistic, and the amount of time required to find a
  given pattern depends on how complex the pattern is, the speed of your
  computer, and whether you get lucky.</p>
  
  <p>The example below illustrates a session of vanitygen. It is typical,
  and takes about 10 sec to finish, using a Core 2 Duo E6600 CPU on
  x86-64 Linux:</p>
  
  <p>$ ./vanitygen 1Boat Difficulty: 4476342 Pattern: 1Boat<br>
  Address: 1BoatSLRHtKNngkdXEeobR76b53LETtpyT Privkey:
  5J4XJRyLVgzbXEgh8VNi4qovLzxRftzMd8a18KkdXv4EqAwX3tS Vanitygen includes
  components to perform address searching on your CPU (vanitygen) and
  your OpenCL-compatible GPU (oclvanitygen). Both can be built from
  source, and both are included in the Windows binary package. Also
  included is oclvanityminer, the vanity address mining client.
  Oclvanityminer can be used to automatically claim bounties on sites
  such as ThePiachu's Vanity Pool.</p>
  
  <p>Current version: 0.22</p>
  
  <p>Windows x86+x64 binaries here. PGP signature here.</p>
  
  <p>Get the source from GitHub. Includes Makefiles for Linux and Mac OS X.</p>
  
  <p>Main discussion at BitCoinTalk</p>
  
  <p>The latest source doesn't work properly for high-end AMD cards (7XXX
  and greater). Solution is to change line 459 in oclengine.c from:
  return quirks; to: return quirks &amp; ~VG_OCL_AMD_BFI_INT; Windows
  x86+x64 binaries that solve this problem plus provide support for
  compressed keys here. PGP signature here. If you have any problems
  with the binaries, join the relevant BitCoinTalk discussion.</p>
</blockquote>

<p>Proper syntax for VanityGen is:</p>

<pre><code>Usage: vanitygen [-vqrikNT] [-t &lt;threads&gt;] [-f &lt;filename&gt;|-] [&lt;pattern&gt;...]
Generates a bitcoin receiving address matching &lt;pattern&gt;, and outputs the
address and associated private key.  The private key may be stored in a safe
location or imported into a bitcoin client to spend any balance received on
the address.
By default, &lt;pattern&gt; is interpreted as an exact prefix.

Options:
-v            Verbose output
-q            Quiet output
-r            Use regular expression match instead of prefix
              (Feasibility of expression is not checked)
-i            Case-insensitive prefix search
-k            Keep pattern and continue search after finding a match
-N            Generate namecoin address
-T            Generate bitcoin testnet address
-X &lt;version&gt;  Generate address with the given version
-t &lt;threads&gt;  Set number of worker threads (Default: number of CPUs)
-f &lt;file&gt;     File containing list of patterns, one per line
              (Use "-" as the file name for stdin)
-o &lt;file&gt;     Write pattern matches to &lt;file&gt;
-s &lt;file&gt;     Seed random number generator from &lt;file&gt;
</code></pre>

<p>The important options to know are -i and -r which cause the search to be case-insensitive and use regex, repsectively. In its simplest format, you issue a command like:</p>

<p>vanitygen.exe 1david</p>

<p>Which tells vanity gen to look for an address with the exact prefix "1david." On a single core of my core i5 this runs at about 325,000 keys per second as shown by the status display (which does show a time estimation.):</p>

<pre><code>[324.43 Kkey/s][total 15166208][Prob 0.1%][50% in 9.1h]
</code></pre>

<p>Using the -i option drastically decreases generation time. vanitygen.exe -i 1david produced the following results in just a few seconds:</p>

<pre><code>Difficulty: 36384905
Pattern: 1david
Address: 1DAVid3iW7XhDBzdoj8FbnaSaqWCjeTgUP
Privkey: 5JvtXtpUbwbNNqRoQjF3w2nyXHhphJk6LX1pWkPYEkBr4nnnBeL
</code></pre>

<p>The -r option allows the specification of a regex value instead of the default pattern option. If, for example, I demanded that my address contain all lowercase letters but I don't care if the "D" in "David" is uppercase or not, I could use vanitygen.exe -r 1[Dd]avid. One downside to specifying a regex prefix is that you will not be given any estimated time or probability data since such calculations are not as trivial as matching a simple prefix.</p>

<p>The more specific your matching criteria (and the longer the pattern) the longer it will take to generate your address(es). This can be sped up considerably if you have an ATI/AMD video card since there is also an OpenCL version of VanityGen which can try millions of keys per second on a decent GPU.</p>
 35507: <p>If you want to create an impressive vanity address, it might be easier to outsource it.
<a href="https://vante.me" rel="nofollow">https://vante.me</a> is a service that calculates Bitcoin Vanity Addresses.
As they use split-key address generation, you are sure that you are the only owner of the private key.
More info here:
<a href="https://www.reddit.com/r/Bitcoin/comments/4iaifs/vanteme_a_secure_and_convenient_service_for/" rel="nofollow">https://www.reddit.com/r/Bitcoin/comments/4iaifs/vanteme_a_secure_and_convenient_service_for/</a></p>
 323: <p>You can generate a vanity address using various generators, such as <a href="https://bitcointalk.org/index.php?topic=25804.0">Vanitygen</a> for example. This option assumes you have a computer with decent GPU, as creating a long vanity address requires a lot of computation.</p>

<p>If you don't have a particularly good piece of hardware and would still like to own a lengthy address, recently split-key vanity address mining became a bit popular. You can use online websites, such as my <a href="https://vanitypool.appspot.com/">Vanity Pool</a>, to request a vanity address to be mined for you for a fee. If you want to understand how this option is possible and risk-free, you can find the discussion of this problem on the <a href="https://bitcointalk.org/index.php?topic=84569.0">Vanity Pool Bitcoin Talk topic</a>.</p>
 2089: <p><strong>!WARNING! The vanity address site below was hacked in December, 2013, but the site owner only recently posted an update admitting the hack: <a href="https://bitcointalk.org/index.php?topic=118968.0" rel="noreferrer">https://bitcointalk.org/index.php?topic=118968.0</a></strong></p>

<p><em>More than 4 Bitcoins total have been stolen to date, as you can see from Blockchain records (note the number of vanity addresses dumping coins, and you'll see that probability alone is proof, supported by all of the users who lost their BTC):  <a href="https://blockchain.info/tx/9e95fd443621d3d9fc150f290144401feb1627573c9161beb08edb472069a819" rel="noreferrer">https://blockchain.info/tx/9e95fd443621d3d9fc150f290144401feb1627573c9161beb08edb472069a819</a></em></p>

<p><strong>The site owner has taken down the site, but for how long is up in the air. As Stack Exchange keeps long archives, I wanted to make sure this warning stuck here for all to see, but did not want to edit the original response.</strong></p>

<p>You can also use <a href="https://bitcoinvanity.appspot.com" rel="noreferrer">https://bitcoinvanity.appspot.com</a>
All done for you on their website and nothing to install.
Is secure as they never know the private key - see help on site for how this is possible!</p>
 1153: <p>I guess you mean Vanitygen:
<a href="https://bitcointalk.org/index.php?topic=25804.0" rel="noreferrer">https://bitcointalk.org/index.php?topic=25804.0</a></p>
<p>From that page:</p>
<blockquote>
<p>Vanitygen is a command-line vanity bitcoin address generator.</p>
<p>Vanitygen accepts as input a pattern, or list of patterns to search
for, and produces a list of addresses and private keys.  Vanitygen's
search is probabilistic, and the amount of time required to find a
given pattern depends on how complex the pattern is, the speed of your
computer, and whether you get lucky.</p>
</blockquote>
