Back in the not so old days, pop stardom was a one-way trip. There was no way for musicians to share information, get immediate feedback, or even swiftly dispel rumors. And outside of the occasional fan club conference, there was no way for devotees to express themselves.

The Net changed that for good. Now artists can reach fans like never before: posting midnight thoughts on the Web, uploading unreleased demos or jumping into the mosh pit of online chat. As for the fans, the Net allows them to completely indulge their obsessions.

Not all artists excel at -- let alone even want -- such intimacy. But the ones who do have spawned some of the most passionate communities, from Prince's Newpowersoul Family to Pearl Jam's Jamily. In some cases, the fans have done most of the work (calling Mr. Slim Shady?).

Either way, here's our list of the most zealous online fan communities.