I first heard about this 'Anonymous' phenomenon on the Warren Ellis blog. They're a group of protestors or hacktivists that have been releasing videos to Youtube and other places and in general causing some small amount of internet mayhem.
You can see an example of the unsettling communications in the blog post linked above in which they protest the actions of the Church of Scientology, claiming human rights abuses and other villainy. They have gotten quite a bit of press due to a denial of service attack that's been executed, bringing down the scientology web site and otherwise clogging up the organization.
What really interests me is their attempt to crossover from an internet phenomenon into the real world. Some videos have indicated that there will be a real world demonstration on February 10th outside many centers of the Scientology organization, and I'm kind of curious to go check out the local one on that day (it's a sunday.) I'm not really big on protests normally, but I think it would be interesting to get pictures and video of this event, if it turns out to be anything at all.
Looks like Google has a picture of the one nearest to me in Farmington Hills: