Well that should be a piece of cake - almost every possible pre-32bit emulator you can think of already exists for the PSP, and you can bet that all of those are going to be available for Linux on the PS3.
SNES & N64 emulators would be perfect. Playing Zelda: Ocarina of time would be awesome, it never gets old.
I wonder will the PS3 be powerful enough to emulate dreamcast even if such emulator would be possible to make? I am simply suffering with my PC even though its only like year old package (bought all the best stuff out there back then) when trying to emulate PS2 or Gamecube. Zelda: Wind waker: 1,5 FPS or so when in gameplay, +60 in movies, not exactly the most enjoyable experience.
My conclusion: I'd expect N64 to be the limit of emulators for PS3.