Everyone's talking about Egytian-style hallucinations got me to thinking about Kenneth Anger's "Lucifer Rising."  Anyway, to the point.

If you're looking for films that mesh well with the psychedelic experience, I would recommend:

The Films of Kenneth Anger

The Films of Alejandro Jodorowsky (esp. El Topo and The Holy Moutain)

Invasion of the Thunderbolt Pagoda

Some notable classics:

Apocalypse Now (The script was originally entitled, "The Psychedelic Soldier" )

2001: A Space Odyssey