A lot of good suggestions already. Here's a few that haven't been mentioned yet.

Cheech and Chong's Nice Dreams (their best, you gotta love the toking iguana)
Help -The Beatles (they were super stoned when making it)
Casablanca (everyone should see this at least once)
Apocalypse Now (imo the best war movie ever)
The Grateful Dead Movie (more of a video than a movie but hey, it's the Dead)
Fengzi Reviewed by Fengzi on . Good Movies ok people im looking for a good movie to watch i can be a drug movie or not i just want a rly good movie to watch so when i do watch i almost shit my pants saying wow that was a good movie Rating: 5