There are a ton of geeks around these days, so this one was tough to narrow down, but when you've got a group whose sole reason for existence is an 11-episode TV series that was axed in 2002, well, maybe it's not so tough after all.
These do-gooder space cases reside in a place called the Whedonverse — named for Joss Whedon, creator of the TV hit Buffy the Vampire Slayer and, more to the point, the character-based sci-fi oater Firefly. The original run of Firefly was butchered by Fox (the network ran the episodes out of sequence) and then unceremoniously canceled, but its fanatical followers, called Browncoats after the lead character's signature duster, have kept its memory alive via good deeds.
Arizona's Browncoats chapter meets monthly for "shindigs" at Bookman's (see www.bookmans.com/events) and also hosts regular Firefly-related charitable events.