HD Channels with a Dish 500 only:
TNT HD
HD Theater (Discovery HD Theater until 9/1/07)
HD Net
HD Net Movies
ESPN High Definition
HBO HD
Showtime HD
HD Event 1. 2 HD PPV (one channel stream with three channel numbers)
Additional HD channels with a Dish 1000/1000.2 or additional Dish 500 pointed at wither 129º or 61.5º
A&E HD
ESPN 2 HD
NFL Network HD
Universal HD
National Geographic HD
Starz HD
Cinemax HD
HGTV HD
Food HD
Golf Channel / Versus HD (shared channel at the source)
MHD (MTV/VH1/CMT combo)
Discovery HD
TLC HD
Animal Planet HD
The Science Channel HD
History Channel HD
TBS HD (that's a joke on us by Turner!)
Big 10 Network HD + 4 alternate channels
NBA TV HD
NHL Network HD
Rave HD (music/concerts)
Equator HD (like Travel Channel)
Gallery HD (fine arts)
Treasure HD
Animania HD (The worst cartoons you have ever seen)
World Cinema HD
Rush HD (extreme sports)
World Sport HD
Ultra HD (Everything you never wanted to know about fashion)
Kung Fu HD (Martial arts movies and more)
Film Fest (More movies)
Monster HD (Horror/monster movies)
HD News
Game Play HD (Like what G4 used to be!)
Family Room HD (Movies and all the Flipper and Thunderbirds episodes you can stomach)
And Your local RSN in HD more than likely.
It's worth getting the new dish.