PS1 ports - Tekken 2, Syphon Fliter, Crash Bandicoot, Medievil, Jumping Flash, Destruction Derby, Rally Cross, JetMoto, 2XTreme, Wipeout, Hot Shots Golf 2, Cool Boarders, and Castlevania:Symphony of the Night. (all these games can be played, upscaled on the Ps3, or transfered to the PSP to be played on there too)
Downloadable Games -
Everyday Shooter,
Go! Sports Ski,
Loco Roco Cocoreccho!,
High Stakes on the Vegas Strip: Poker Edition,
PixelJunk Racers, Super Puzzle Fighter 2 Turbo HD Remix (no link required, I assume),
Tekken 5: Dark Resurrection,
Warhawk,
Piyotama,
Gripshift 2.0,
Nucleus,
Super Stardust,
Go! Puzzle Game (there are two more types of puzzle games in this one game, but I could not find an adequate trailer),
Championship Sprint, Joust, Rampage: World Tour, Rampart,
Calling All Cars,
Super Rub-A-Dub, Gauntlet 2, Mortal Kombat 2, Gran Turismo HD 1.2 (free but content bare),
flOw, Q*Bert, Go! Sudoku, Lemings,
Blast Factor, and
Cash Guns Chaos DLX
I have warhawk, everyday shooter, and calling all cars and can tell you that they are all very high quality games. Everyday Shooter may SEEM like it is just geometry wars (actually, a lot of the games on there seem like geometry wars/robotron), but it is much more reliant on the music in the level you are playing (each level has different music) to help string together combos and kill off the mass amounts of enemies streaming at you. There's no big "oh shit" bomb to kill everyone on the screen, so you have to rely on the nuances of the game to survive. It's super hard and Im terrible at it, but the graphics and sound design are so stylized that it's hard to ignore once it's in your library. I don't have any of the PS1 games, but I soon wish to own Jumping Flash, and I'll tell you how the ps3 looks with it and the psp.
Also, there's an interesting function on the ps3. Along with the 360-like ability to watch certain video files (in this case mpeg-4 I think) from your PC on the ps3, you can stream them to your psp over the wireless internets. So if you're at university or work or whatever, and you want to watch some harvey birdman or venture brothers episodes, you can whip out the ol' psp and as long as you've got your ps3 and computer still running at home, you can watch movies to your heart's content. I thought this function was a little nifty.