Twitterific - Reading / Posting Tweets
Shazam - Tells you what song is playing by holding it up to the speaker
Sonic Lighter - Silly lighter app that has a global picture of how many people are using it, really geeky but cool
Facebook - Stalk people while you are on the can
Wordpress - Blog while you are on the can
iTalk - Very handy voice recorder
Flixster - Movie showtimes, trailers, & box office info
Backgrounds - Nice background downloader, lots of new ones all the time (free)
Scribble - Awesome MS Paint-style app, you can even edit your pictures you just took w/ the camera
And finally, PBJTime, because sometimes you just need to annoy someone.