These are all the ones I have at the moment. I've indicated those I think cost me a buck or three:

APPS

All Things Digital - Tech news
Amazon Mobile
AOL Radio
Baseball
Card Shark Solitaire premium [$]
Chirp! Bird Songs USA [$]
Cowbell Plus
Drums Challenge [$]
Emergency Radio [$] - pretty neat
Epocrates [$?] - medical app for Rx drugs
F-MyLife - Pretty funny
Facebook
Flashlight
GigBabyFree! - 4-track recorder that didn't work when I tried it
Google Earth
Google Mobile App
Holy Rosary Deluxe
Homes.com real estate
i.TV - TV listings
iHandy Level Free
iTrans NYC Subway [$]
Live Poker by Zynga
Loopt
Mafia Wars 20 Reward Points - lame compared to Facebook version
Mark of Mafia! FREE - been playing since January
Mediafly: Video + Audio
Movies (Flixster)
MySpace Mobile
Paper Toss [$?]
PayPal
PhoneFlicks - Neflix
Pocket Universe [$] - ID the night sky, pointing to stars - Amazing!
PocketGuitar
Puluwai Free Real Estate
Pure Sleep | AmbiScience
Real Estate Search (Blue Atlas)
Shazam - Supposed to ID songs you hear, but doesn't work often enough
ShopShop - Shopping list
SIRIUS XM Premium - Stream satellite radio; free app, but monthly fee
Skype
SportsTap
TwitterFon
USA TODAY
Virtual Zippo Lighter
vSNAX Videos
The Weather Channel
1Password
300 Bowl

WEB APPS

ESPN
Live Scores
TV Guide
eBay
iRadio
Mobile Pod
Britanica
TippyTops (tip calculator)
Guitar Tuner
Ruler
FlightView - plane flight info