Hmm... in no particular order, here's how I live:
1. Last.fm so that I can have music without downloading.
2. Pages '08, I wish I had '09 but this is school provided (my MacBook is school provided actually)
3. Keynote '08 totally blasts PowerPoint out of the competition. I use this biweekly for school presentations.
4. Firefox, don't know why I would have a Mac without Firefox.
5. ShoveBox for throwing bits of information.
6. Anyone mention Growl? Coming from a Windoze world (how I hated that slow box) I have the preference of full screening every window ingrained (thank you so much Microsoft, I'll donate -1 billion dollars for that) so Growl helps me notify me of mail, news (via Vienna), Skype, and tons more.
7. Namely is another app launcher, though not as good as QS, but it's sufficient for me. Nice thing that Namely does is nothing. Almost no system resources, no clutter, just a search bar that can be called up, customizable, and free.
8. The Hit List for my GTD, soon to be Actiontastic or ThinkingRock or RTM when THL becomes ver. 1, currently ver. 0.9.
9. Thunderbird for mail. 'nuff said.
10. Skitch for simple image editing. Can't use PS so I'll use Skitch. Suits all my needs for now.