Yeah, there are movies that are in and of themselves psychedelic in the way they're filmed, and then there are movies that are better appreciated while on psychedelics, and I'm not sure how much overlap there is between the two. I wouldn't abide 'The Cell' played in my house if I was tripping, except maybe the parts with J.Lo as a shrink in a really short skirt.
Three Caballeros -- I picked up a bootleg copy of this classic Disney movie when I was in Taiwan, and now I've lost it. I need to get it for next time I take LSD. It's probably the most psychedelic work Disney ever made. Highly recommended if you've got an hour of tripping time to spare, and don't mind Latin music.
There are a few other Disney movies that contain psychedelic scenes in the same style as Three Caballeros, before returning to a normal plot. The 'Elephants On Parade' dream sequence in Dumbo is one. Can anybody name any of the others?