http://en.wikipedia.org/wiki/Canterbury_scene
All of that. But for specific recommendations, Khan's only album is wonderful. Gong's later stuff, especially Shamal, is great, while their early stuff is definitive psychedelic rock. Soft Machine and Caravan are also fantastic.
Moar excellent prog rock: Yes, Uriah Heep, King Crimson
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Guru in a half-shell. BlAcK TuRtLe power!
If there is one thing I know, it is that I know nothing.