Rush & Yes to a certain extent.
Anyone heard a 70s band called Patto? That band had the most amazing guitarist (I may have posted about him before) named Ollie Halsall. That bastard taught himself to play guitar after playing the vibes and piano- he figured he played a lot of intricate stuff on piano with his right hand, so he should play guitar using that hand, & played left handed (this was when he was like 19 or so). Anyway, they sounded sort of like a mix between Humble Pie, Yes, Zeppelin, and something more artsy/jazzy. Lots of long-winded instrumental jam passages with vibes and stuff, but also lots of riff-rockin' classic rock stuff with cool time changes thrown in.
Now that I finished typing this, I do believe I did post this already. My bad.