Head http://www.imdb.com/title/tt0063049/
This is the most psychedelic movie I've seen or know of. I just watched it again and I'm sure it's one of my top favorite movies, maybe the best movie ever. It's left very wide open for interpretation of what it all means (if anything), but it's very intelligent.
Of course I can't forget to mention that Dimension 5 sampled "Observe, and act with clarity" from the movie in Deep Space 5D.
I think you should all watch it, you won't be disappointed.