Spaz notes:
King's X: fantastic three piece with ridiculously complex arrangements, but it doesn't
sound complex. But just try to learn it and play it.
Ten Years After: Killer pseudo-psych jam.
The Sea and Cake: Often called post rock, but more of a pop-rock, artsy version.
Asia: Pop prog supergroup.
Anton Rubinstein: Russian Romantic composer
The Choir: Killer, weird 90s alternative. Crazy percussion and a Kenyan whistle. For a low budget, DIY video, check this out:
Sled Dog
Punch Brothers: Sometimes called the world's first progressive bluegrass band. Traditional bluegrass instruments, but not bluegrass.
The Who: Mod-rock, proto punk
Sixpence None the Richer: One of the great below-the-radar 90s alternative bands. Unfortunately pigeon-holed as a bubblegum band because of one uncharacteristic pop hit in "Kiss Me."
The Jimi Hendrix Experience: Slightly psychedelic blues rock