There's a bunch of popular emulators for PS3. Unfortunately, no N64 emulator is working to date. The most popular are FCEU (NES), SNES9x (SNES), Gens+ (Genesis), and VisualBoy Advance (GBA). These emulators all have versions available that can be managed with MultiMAN, one of the more popular game managers out there. Once set up, they all work great, though they lack any tactile GUI without MultiMAN involved. (Personal opinion. I really would prefer GUIs similar to the emulators GX counterparts on Wii.) Anyway, I'd provide a bunch of links, but I'm at work and don't have time. Google the emulator names, followed by PS3, and you should get some good results. There may even be some topics around here with downloads to them. (If not, I may spend my downtime tomorrow compiling some files for you. ) Anyway, that should be enough information to get you started.
Also, I highly recommend transferring your ROMs to the PS3's internal HDD, and setting your save locations to be on the drive as well. (There are tutorials floating around that you can get the bits and pieces of, but I think I just found another project for myself. )
Actually, if someone can post links for all working emulators I would like that. There's so many links out there and the emulator side of the PS3 (well PS3 hacks in general is kind of cold right now) with bunch of fake ones / imitation ones....it'll make my part easier, along with getting the current version