As has been mentioned this is a massive subject, but as a tangent to the Incredible String Band suggestion, one that's been growing on me lately is the Sun Also Rises LP from 1970. They were definitely ISB influenced, but in a good way, sort of "ISB Lite". It's one of those LPs that might not grab you at first but gets a bit richer with repeated plays.

Oh, and the group name is a pun of sorts. The group is fronted by a couple surnamed Hemingway...

Steve Canner
The Victor Mourning
Maryville, Tennessee
http://www.thevictormourning.com