Here's a couple favs that I use regularly

Weird Facts
Pandora (music)
Word Feud (scrabble) - Justahobby is my screen name, play me!
Daily Bible
Dictionary
Aldiko (free books)
Drink Malk (catalog w/ every book imaginable added to aldiko. PM me and I will send you the directions)
GTunes (mp3 songs free, huge selection)
Ring Tone (let's you edit the ringtones too!)
ProjectINF (multiplayer shooting game)
Science Mobile
Angry Birds
Animal Planet