Here's a word I've been confused about a long time. I use both - depending on the situation, and when I use the latter spellcheck always tells me I'm wrong. Sometimes I let it fix things for me, and sometimes I don't, because the way spellcheck claims is right just doesn't feel right to write.
I finally decided to once and for all find out who's right and who's not, and it turns out... both are correct, though according to many an authority and language blog: among is the preferred version, since amongst sounds old-fashioned and out-of-tune. Oddly enough, amongst is actually the newer word of the two, and though not as common as among, it's still commonly used despite all the authoritative critique. In UK English it's a tad bit more accepted than in the US, too.
So there you have it! There's some wisdom amongst these pages of teh Interweb after all! I guess I'll keep shillyshallying between the two whenever there's opportunity to.
Among err, a monger of grammatical justice stirs.