http://www.youtube.com/watch?v=SnqlfGU4ij0
Laughter is a strong and common mind alter-er.
Here, a whole car on a subway gets a strong mind alteration by making each other burst into laughter, giving everyone around a raise in endorphins. Even watching the video gets the watcher into another, humorous consciousness. Prepare for a gleeful, substance-less high (Except for the chemicals of pleasure in your brain, of course).
The Daily Psychedelic Video 