Cherry Roms is pretty good (do a search) - you'll probably have to sign up (it's free), but it has a wealth of SNES games.
Personally I can't be bothered with PC based SNES emulators - control pads are pretty much vital for snes games. If you want a real and pure and wholesome emu experience, get hold of a second hand Dreamcast and DreamSNES (dcemu.com), quite possibly the ideal SNES emu solution because the control pads are fairly identical, your playing on a TV, and the 4 dreamcast controllers are all supported.
Van-B
The nature of Monkey was irrepressible!.