Been listening to a lot of instrumental post-rock and math-rock stuff lately (easier to listen to while working).

God is an Astronaut

(just got a copy of their discography the other day ... all excellent stuff)

Pelican

(a little heavier than the others)

Don Cabellero

(who frankly have the coolest song names ever)

Oh and The Fu*king Champs

(also heavier and with more of a sense of humor)