Four of us are trying an experiment with GMing a shared campaign. The way it works is, each of us takes a turn running a scene (expected to be around a month play-time) before handing the reigns over to the next in line.
We are starting at first level and each GM develops that chunk of the world that they need for their stint. Each player also creates whatever aspects they require, or are interested in with respect to their characters. For example, you want to make a paladin? Then feel free to create the deity, church, supporting NPCs, city of origin, etc etc. The characters and the plot and the world all evolve in an organic manner that we think should be quite interesting.
Ideally, we would like a couple more players, people who are creative and willing to shoulder some of the world-building/GMing responsibilities. Please post here with a character idea if you are interested in joining us. We currently have a ranger, cleric, paladin and witch. 25 point buy, core and APG classes/races, limited item creation feats.
Cheers!