There's an (incomplete) list of professional MMA fighters by BJJ belt rank at the following link:
http://www.bjj.org/a/mma.html. Notable UFC names appearing on this list (aside from those mentioned in my previous post) include Pat Miletich, Matt Serra, Elvis Sinosic, Brandon Vera, Vitor Belfort, Anderson Silva, and Nathan Marquardt. Frank Mir is listed as a brown belt, but I think that he's since earned his BB.