What are your must-have apps?
christefano:   Quicksilver
The quick application launching and various file and text manipulation actions are great, but it's the multiple clipboards that I find invaluable. Being able to save and search through 500 clipboards makes Quicksilver the one greatest productivity tool I have.  iTerm
Multiple profiles, full screen mode, sending commands to all open tabs, etc. make it a better terminal than Terminal.  Adium
It doesn't have video chat yet but I don't mind. It does everything else I could want an IM client to do and the OTR encryption works right out of the box. Plus, the next version reportedly supports both Twitter and IRC.  Navicat
It's the best tool I've seen for accessing remote databases (I use the MySQL version for Windows running in CrossOver). Sequel Pro and Querious both win on looks but Navicat has the features I need.  Drupal
Drupal is known for being a good content management system but for me it's an absolutely great web application framework. It does nearly everything I need my websites to do, from running wikis and OpenID providers to large social networks, project management platforms, ecommerce sites and virtual worlds. The Drupal community is so large and diverse that the conferences, camps and user groups are the best I've seen around any industry or software project.  Virtualmin and Webmin
These are web control panels like cPanel and WHM that are available as a free, GPL version or as a commercially supported "Pro" version. I think Virtualmin is a YC startup, too. Virtualmin and Webmin are occasionally a little rough around the edges but they have completely taken away the pain of administering my sites.  GrandCentral
It used to be that using voicemail was a necessary time expenditure that nobody really questioned. GrandCentral saves me a lot of time I'd otherwise be wasting.Here's a tip: don't upgrade your GrandCentral account to Google Voice unless you want the stuff that only Google Voice has (like voicemail transcription). All the GrandCentral-compatible tools like GrandCentral Dialer for the Nokia N8x0 tablets don't work with Google Voice yet.