Well, a lot of reference stuff (Dictionary, WoflramAlpha, etc.), FaceBook, Texting stuff, a whole lot of games, a few photo editing apps, some music-related stuff (Pandora, instrument apps), comics (AMD 1, 2, and 3, Cyanide and Happiness, XKCD), and just some entertaining apps, like iLaugh, TFLN, and I Can Haz Cheezburger.
The ones I've said here aren't all of the examples. But yeah, mah iPod is mah buddy.