http://www.grizzlyman.com/
I just checked this out today. I remember reading about it last Summer when he died, but I didn't really know much else about it. It's a pretty cool documentary, made by Werner Herzog, based mostly on the 100 hours of video footage left behind by Treadwell, intercut with interviews with people who were close to him.
Whether you agree with what he was doing or not, it's a fascinating look into the 13 years Treadwell spent with the bears.