well of course you've gotta get a drawing app! Sketch Club is a great one to check out since it has the traditional brushes as well as fun procedural brushes and also has the nice online gallery, community and competitions.
you'll also want IM+ for instant messaging, penultimate for note taking, netflix as already mentioned if you have an account, Friendly for facebook-ing, NPR app for news and radio shows, oh and Pandora of course.
for games you should check out Infinity Blade (gorgeous Unreal Engine game - though looks better on iPhone 4), Angry Birds, Pinball HD, Fruit Ninja, Spirits, Arriving HD, Cut the Rope HD, and SimCity DLX!
AskLocal is a nice app for the iPad as it makes extensive use of maps and looks better on the larger screen.
It's a way of posting messages pinned to locations on a world map. Doesn't seem like a big deal at first, then the possibilities hit you when you realize you can limit who can see/reply to your messages based on their physical distance from each of your messages.