Alan Watts - I recently got an email off someone thanking me in the most enthusiastic terms for introducing him to The Voice Of Clarity. I suggest you search out some of the podcasts which are available to subscribe to via iTunes. They make for good relaxing rambles.
Robert Anton Wilson - Pope Bob. Robert Anton Wilson is the unassuming granddaddy of them all. Search out the film "Maybe Logic" and give it your time. He's also a great writer, Cosmic Trigger, is one of the best esoteric books I've read. His genius sneaks up on you like a thief in the night.
Captain Beefheart - finest vocal chords ever to tackle psychedelica.
John Martyn - now that's how you play a guitar.
Eris - Hail.