Well, I'm not sure if these truly count as "Fringe", though I'm not sure if we have a formal definition anyway...
These are bands I don't often find other people know.
The Seatbelts: Rush
Mostly Jazz, Most of their music is used for the soundtrack of the Anime Cowboy Bebop
The Afro Celt Sound System: Colossus
Celtic-ish, with African drum rhythms (see Riding the Waves)