my favorites are iVote, a social networking app where you answer questions then comment on them. Palringo IM, an IM app that supports push notifications. 1Password, an app that stores all of my passwords securely. eBay, I sell stuff on eBay pretty regularly, so it's pretty useful. Skype; make VOIP calls and IM. Math Solver; solves virtually any mathematical equation, and gives you the steps involved. X-Plane flight simulator. Nanosaur 2 by Pangea software; flying shooter game. Toy Bot diaries; comes in three parts. You have to navigate through a maze using your little character's special abilities. Guitar Rock Tour; kind of like guitar hero. Blue Skies; 2d airplane shooter. And, Monopoly by EA.
That's my favorites. I've got about 90 other apps on my iPod too, but I don't use them as often.