Anything by Ed Wood, though 'Plan 9 From Outer Space' is (of course) his best/worst film, and for good reason. I love blaxploitation flicks too, did a big essay on them for my Film Studies course a couple of months ago. If you haven't seen 'Blacula', you really should. It's actually pretty damn good!
Finally, 'Sweet Sweetback's Baadasssss Song'. It's fun just listening to the stories involved with its production, such as Melvin van Peebles (the director/star/everything else) pretending it was a porno to avoid the unions, contracting gonorrhoea from an unsimulated sex scene and claiming benefits for being injured to help funk the film! Absolutely mental...