Just a few I use regularly:
Firefox
Fetch (for S/FTP)
TextWrangler (the bomb for text editing or programming)
Lightroom and/or Aperture (I have both, wanted to compare)
Burn (if you still do that kind of thing)
Disk Inventory X (great for analyzing your disk space)
Dropbox (my flavor of cloud storage)
Gimp
Your choice of office suite (I personally use MSO even though I hate MS but also have iWork and OpenOffice)
mSecure (my flavor of password vault)
MS RDC (if you remote into any MS boxes for work or home)
VirtualBox by Oracle (if you wish to run any virtual machines from your MBP)
Smart Converter Pro (convert video from your DV-cam to any format you wish)
iShowU (good screen capture app for producing instructional/training videos, etc.)
iTerm (great terminal emulator app, though you can also use the native "Terminal" app)
Keyboard Maestro (for any keystroke macros you may wish)