The religions listed here are not a joke. Each one of them is a real religion with actual followers. You are more than welcome to add to my list. Try to add religions no one's ever heard of, and that people might think would be a joke if it weren't real. Just don't be a smartass and say "christianity" or something like that...
razz Perfect Liberty KyodanThis is a Japanese religion that focuses on golf as a spiritual act. Golf is a form of art and life is about being as artistic as possible.
part 1 part 2
Cargo CultsThis is a religion on some islands in the South Pacific, focusing on praying to a god named John Frum to bring cargo from ships to the natives of the islands. Not having factories, the first time the natives saw ship cargo, they assumed it was a gift from the gods. John Frum was one of the only men to freely give the natives cargo they wanted, and has since been elevated to godhood by these people.
part 1 part 2
Hot Tub Mystery ReligionThis religion is all about sitting in a hot tub and talking about the dogma and beliefs from other religions. Nitrous Oxide is a holy sacrament, and the jacuzzi parties thrown by the followers of this religion can be seen as religious gatherings.
http://www.reason.com/0305/fe.jw.inside.shtmlThe Church of SubGeniusLike Discordianism, this is another religion that started as a joke but took on true followers. (In fact, SubGenius and Discordianism can be seen as sister religions.) Being a follower of this religion, part of the SubGenii, is easy! All you have to do is have an IQ level below that of a genius.
http://www.subgenius.com/