Cracked.com (which may be related to the weirdo teenage humor magazine of the same name) has presented a list of ten celebrities who, for better or worse, have embraced the writings and theories of L.R.R. Hubbard and gone the way of Scientology. There may be the occasional joke here or there, but I've confirmed enough of these to believe the list is genuine (exempting, perhaps, Bart Simpson).
I've never been ambiguous on my opinions about Scientology, but this is neither the time nor place. I'll merely post the link for your enjoyment:
Top Ten Secret Celebrity Scientologists
1 hour ago