UbuWeb is something Archive.org but geared entirely toward avant-garde works. They have a huge film and video archive as well as audio and text/print documents of various kinds (even criticism). It’s a strange landscape, worth getting lost in. I’ve barely put my toe in the shallow end of the pool, but this 60s video of Raashan Roland Kirk playing along with some John Cage voice overs (spliced in after the fact) was a thought provoking start.