What do you usually use for:

Operating System: (Mac) OS X – Tiger
Screen Resolution:1280×854
Web Browser: Firefox

E-Mail: GyazMail – ok, I still and forevermore regret the loss of Agent for email. But GyazMail isn't bad. I find it's more powerful than Mail (the native mac program) but it doesn't have Mail's smartfolders. Er. I don't actually remember why I like it better than Mail, but I do. It's still not Forte's Agent. <sob> (Please, please, please you guys, develop an OS X version. But don't tie it to the intel chip.)

Word Processor/Office Program: NeoOfficeJ – perfectly good office suite, opens and will save as word/excell files. OpenOffice is also available for Windows.
Text Editor: TextWrangler

Instant Messenger: Adium (does AIM, YIM, MSN, ICQ, Jabber, Google Talk, Bonjour, Gadu-Gadu, Lotus Sametime, Novell GroupWise)
Image Editing/Manipulation: iPhoto and ::shudder:: Gimp. I'm seriously considering now using Photoshop Elements.

Media Player: iTunes and QuickTime
LiveJournal Client: xJournal
DVD Watching: DVD Player (Mac program)

And I'm adding these:

IRC: Colloquy – because Adium doesn't do IRC yet
Finances: Moneydance – fantastically better than ::shudder:: gnuCash, and just as good as Quicken, without getting raped by Intuit. Also available for 'nix and Windows.

HTML Editor: Taco HTML Edit – cute little HTML editor when you're too lazy to use TextWrangler. (Which, btw, would be a fantastic tool for writing web pages if I was a little less lazy about it)
RSS Aggregator: NetNewsWire – fantastic RSS reader. Will import podcasts into iTunes as well. Also, it will post news articles directly to various flavors of journals, LJ included.

FTP: Cyberduck – yeah, so I'm too lazy to learn the ftp command line. This is a pretty good program for ftp.