Some good recommendations, and some shitty ones...
I'm gonna be a dick and mention 4 bands:
Minus the Bear, which was mentioned in another thread recently. Go see them live, they're orgasmic.
[ame=http://www.youtube.com/watch?v=Kols9wQQPzs]YouTube - Minus the Bear - "Knights" Suicide Squeeze Records[/ame]
Explosions in the Sky
I got to see them for my first time this summer in their home town of Austin. The band every post rock fan should know.
MP3 Search - Mp3Search.fm
Lotus
Lotus is one of the first "jazz" groups I got into outside of the classics, and I can safely say its changed my view on music all together. Their later stuff gets a bit more funky, but all of their music is totally danceable.
[ame=http://www.youtube.com/watch?v=1syZXrL9WA4]YouTube - Lotus - Spiritualize[/ame]
The New Deal
Lotus' less attractive cousin, but I'd still tap it. Lots of jam band and jazz influence.
Nothing worth linking to, but PM me if you want some of their stuff.