Braingle
So who is this guy, you ask, who spends all this time working on Wikipedia? I'm mainly a content contributor, although I do other things, including reverting vandalism, assisting other Wikipedians, etc. Here's a list of articles I've written and edited.
I first edited on Wikipedia in December 2008, and was immediately enthusiastic about this huge project. The possibilities of the project for growth, for dissemination, for quality, and for just having fun, for any intellectual person who likes to write and happens to have some extra time, were enormous; indeed it was one of the first places I had ever found on the Internet that didn't feel like another few electronic acres of wasteland. Some may think I'm nuts for spending so much time writing an encyclopedia, but I tell you it's exciting to see one's articles shoot to the top of Google rankings shortly after their creation. Not only do I find it exciting, but I increasingly find it to be my duty, as someone having a specific expertise, to put accurate, readable, and well-sourced information into that top Google position.