I'm sure you've heard, but if not, Disunplugged has an app for WDW.
I just got my first smart phone (3gs) last December and, like you, am looking for apps.
You might like: Red Laser (use the camera on a barcode for a product and it'll search out the best price); Kindle, iBooks (works great if you need or want to read pdf's on your phone. I just installed Room77 (a fellow poster mentioned it).
Of course, most of the news sites have their own apps including USA Today and CNN.