user1888: Let's say I have 10 bitcoins. I won't be using 8 of them any time soon. How can I put the 8 in a separate "offline" wallet not related to the bitcoin client?
This would be a good security measure. If the bitcoin client is ever compromised, only the remaining 2 bitcoins would be at risk.
It seems rather reckless to have all of one's savings in the same wallet.

user1947: I recently created a blog post about this: https://bitinnovate.com/creating-an-offline-bitcoin-wallet/
Steps for creating an offline bitcoin wallet

Open the folder that contains your wallet.dat file

For Windows users: Go to Start -> Run (or press WinKey+R) and run this: %APPDATA%\Bitcoin
For Linux users: By default you Bitcoin should be here: ~/.bitcoin/
For Mac users: By default you Bitcoin should be here: ~/Library/Application Support/Bitcoin/


Back up your wallet.dat file to a secure location
Move your origional wallet.dat file out of this directory
Start the Bitcoin client
The Bitcoin client will automatically create a new wallet.dat file and a new address
Copy the address and save it in notepad
Encrypt the wallet with a secure passphrase
Close the Bitcoin client
Go back to the Bitcoin folder
Move the new wallet.dat file out of this folder and store it somewhere safe. I suggest making multiple backups of this on multiple media types. I.e. CD, SD Card or a portable hard drive
Move your old wallet.dat file back into the Bitcoin directory
Run the Bitcoin client
You can now send bitcoins to the address you copied down and they will be securely stored offline

To get the offline wallet back online. Move out the existing wallet.dat file and replace it with you offline file. Open the Bitcoin client and you will now have access to the bitcoins associated with that wallet.

user-1: 
You better use off-line machine for generation secure bitcoin
address. (see vanitygen)
Thereafter send your money from on-line machine to this address.
Bitcoin now are safe.
Nobody know your private key.


user323: 
Go to your Bitcoin data directory
Backup your wallet.dat to a safe location
Move your wallet.dat away from the data directory
Start Bitcoin. It will create new wallet.dat
Get an address from the new wallet, save it in notepad
Encrypt the wallet with some passphrase you will remember for a long time
Turn Bitcoin off
Go back to your Bitcoin data directory
Take the new wallet.dat and store it somewhere safe
Move your old wallet.dat file back into the data directory
Run Bitcoin again.
Send 8 Bitcoins to the address you saved in notepad

Now you have two wallet files - one with 2 bitcoins for your normal use, one with 8 bitcoins for keeping them safe. Just make sure not to lose either of the two wallets, or you'll lose your coins.
Keep your wallet.dats backed up and don't run duplicates at the same time.

1888: <p>Let's say I have 10 bitcoins. I won't be using 8 of them any time soon. How can I put the 8 in a separate "offline" wallet not related to the bitcoin client?</p>

<p>This would be a good security measure. If the bitcoin client is ever compromised, only the remaining 2 bitcoins would be at risk.</p>

<p>It seems rather reckless to have all of one's savings in the same wallet.</p>
 1947: <p>I recently created a blog post about this: <a href="https://bitinnovate.com/creating-an-offline-bitcoin-wallet/" rel="nofollow">https://bitinnovate.com/creating-an-offline-bitcoin-wallet/</a></p>

<h2>Steps for creating an offline bitcoin wallet</h2>

<ol>
    <li>Open the folder that contains your wallet.dat file
<ul>
    <li><strong>For Windows users:</strong> Go to Start -&gt; Run (or press WinKey+R) and run this: %APPDATA%\Bitcoin</li>
    <li><strong>For Linux users</strong>: By default you Bitcoin should be here: ~/.bitcoin/</li>
    <li><strong>For Mac users:</strong> By default you Bitcoin should be here: ~/Library/Application Support/Bitcoin/</li>
</ul>
</li>
    <li>Back up your wallet.dat file to a secure location</li>
    <li>Move your origional wallet.dat file out of this directory</li>
    <li>Start the Bitcoin client</li>
    <li>The Bitcoin client will automatically create a new wallet.dat file and a new address</li>
    <li>Copy the address and save it in notepad</li>
    <li>Encrypt the wallet with a secure passphrase</li>
    <li>Close the Bitcoin client</li>
    <li>Go back to the Bitcoin folder</li>
    <li>Move the new wallet.dat file out of this folder and store it somewhere safe. I suggest making multiple backups of this on multiple media types. I.e. CD, SD Card or a portable hard drive</li>
    <li>Move your old wallet.dat file back into the Bitcoin directory</li>
    <li>Run the Bitcoin client</li>
    <li>You can now send bitcoins to the address you copied down and they will be securely stored offline</li>
</ol>

<p>To get the offline wallet back online. Move out the existing wallet.dat file and replace it with you offline file. Open the Bitcoin client and you will now have access to the bitcoins associated with that wallet.</p>
 -1: <ol>
<li>You better use off-line machine for generation secure bitcoin
address. (see <a href="https://github.com/samr7/vanitygen" rel="nofollow">vanitygen</a>)</li>
<li>Thereafter send your money from on-line machine to this address.</li>
<li>Bitcoin now are safe.</li>
<li>Nobody know your private key.</li>
</ol>
 323: <ol>
<li>Go to your <a href="https://en.bitcoin.it/wiki/Data_directory">Bitcoin data directory</a></li>
<li><strong>Backup your wallet.dat to a safe location</strong></li>
<li>Move your wallet.dat away from the data directory</li>
<li>Start Bitcoin. It will create new wallet.dat</li>
<li>Get an address from the new wallet, save it in notepad</li>
<li>Encrypt the wallet with some passphrase you will remember for a long time</li>
<li>Turn Bitcoin off</li>
<li>Go back to your Bitcoin data directory</li>
<li>Take the new wallet.dat and store it somewhere safe</li>
<li>Move your old wallet.dat file back into the data directory</li>
<li>Run Bitcoin again.</li>
<li>Send 8 Bitcoins to the address you saved in notepad</li>
</ol>

<p>Now you have two wallet files - one with 2 bitcoins for your normal use, one with 8 bitcoins for keeping them safe. Just make sure not to lose either of the two wallets, or you'll lose your coins.</p>

<p>Keep your wallet.dats backed up and don't run duplicates at the same time.</p>
