TOD:
I agree about so many of the documentaries that were mentioned. In addition one of the favorites of the few that I actually saw in a movie theater was the one about the career (to that point) of Bruce Vilanch, called GET BRUCE. Hilarious and very moving at times.
On a related note, I also enjoyed MAN OF THE YEAR, made by a Playgirl centerfold-turned-director about his experiences being a centerfold. I saw it very early on, so I was totally fooled by this one, thinking it was a documentary that happened to have a lot of humor, but realized only about two-thirds of the way through that it was closer to a mockumentary. Very entertaining.