If you want more music like Bitches Brew, don't look at free jazz or avant-garde. It has vague elements of them, but it's mostly just early fusion.
But if you do want free jazz:
Cecil Taylor - Unit Structures
Ornette Coleman - Free Jazz
Sun Ra - Space Is The Place (or anything, I guess; it's the only one I have of his)
That's about as essential as it gets. Sonny Sharrock has some good fusion free jazz that's closer to Bitches Brew, but I don't really know him well enough to point out records.
As for
good fusion (not easy to come by), a lot of the people that play on Miles' fusion stuff--Herby Hancock, Chick Corea--have stuff of their own that you might like. Also, try Hiromi's Sonic Bloom. Not free jazz at all, but fucking awesome stuff.
Here's some of it so you don't get something you don't end up liking. It's kind of different.