Zophar's SPC archive - Biggest collection of SPCs from almost all games for this console
SNESamp Archives - Another cool quality collections, all the song are tagged with ID666 tags.

Some more thoughts

Do you like the game music filled with unforgettable "japanese" sense and athmosphere? Then Super Nintendo tunes would be really thing you should take closer look at, if you don't like to download big MP3s from original soundtracks (see below). But let's talk something about some facts of Super Nintendo's tunes. Super Nintendo Entertainment System (SNES in short) was 16-bit game console which had most popularity in early 90s, so we can compare the quality of music with Amiga. Although Amiga was more popular in Europe, SNES and Sega MegaDrive have been very popular especially in Japan. Games on this console are mostly japanese too, and the same is it with music. SNES got its fame with two types of games - RPGs and Jump'n'Runs. In RPGs was absolute leader Final Fantasy serie also due to its music done by Nobuo Uematsu. But another ones - Chrono Trigger, Illusion of Gaia, Soul Blazer, or Tales of Phantasia have all "typical" japanese feeling, which is hardly to describe, better is to listen to it :). In Jump'n'Run genre is most famous Nintendo's Super Mario, but also some european companies converted on Super Nintendo from Amiga and started to do quality games (for example Factor 5 company did this, so we can hear Chris Huelsbeck's production like Super Turrican 1&2 or Indiana Jones for SNES). And we sure cannot forget japanese Jump'n'runs - especially Konami's games have great sound, my personal favourite is Castlevania (and all sequels). If I compare the Amiga and SNES tunes, I prefer Amiga ones (I see more "melodies" in Amiga's tunes and maybe it's also because SNES tunes are often "too japanese" :) ). But it should be only my opinion, you should try and listen to SNES tunes, at the links below are very much SNES tunes in very good SPC format (every tune has only around 60kB), you will sure have fun listening to them.

Players and other useful links

Super Jukebox - IMHO the best player for SPC files
Other SPC players - If Super Jukebox won't satisfy you :)