I have a special fondness in my heart for movies such as these.
Note: I don't think these movie are really very successful. It takes a lot more work to make an actual story that contains all the messages and themes you're trying for, as subtext. Making it blatant with "avant garde" imaging always seems like laziness to me.
Doesn't mean I don't enjoy these movies. I like them quite a bit.
There's always the Monkee's HEAD. Pretty entertaing slice of 60's cinema. I don't know if Abby is still around, but she could say a thing or two about this movie.
And if your really want to go off the damn wall, you could watch
Greaser's Palace. But that movie really begs the question, is it a concept/message movie if nobody can understand what the hell they were trying to get at?