Perpetual Groove. Some call them a jam band, I just call it SPECIAL/original music. (They are NOTHING like Phish/Grateful Dead, don't worry. Just Grade-A Rock).

http://www.rhapsody.com/perpetual-groove

Just click through the box that comes up, it will let you listen for free. Please at least just give TSM2 a go...if you like that, check out Only Always, Save for One, Mayday if you want something a bit harder, Long Past Settled In, Three Weeks, it's all amazing.

They also do some of the best covers I've ever heard a band do...ie., this solo acoustic performance by the lead singer/guitarist, Brock Butler, of T.I.'s "Whatever you Like". Done with loops, all by himself, in a small club in Richmond. http://www.archive.org/details/brock2010-07-22.flac16 (Track 8)

And oh-by-the-way, they tour relentlessly, never stop a show before 2am unless they're forced to, and no one show is ever the same. They will often take a 6 minute song and turn it into a 15 minute one live, which is the only reason some people call them a "jam" band...but its no mindless jamming.