Mashupcamp II is an unconference I attended on Wednesday and Thursday. What is an unconference? It starts with a website where you register to attend or in my case a waiting list to attend. The cost is free. However, I turned up as instructed and got in early Wednesday.
What happens is that a wall is covered in white paper where an empty schedule is grided out. Then those attending are free to write up a topic for discussion in a room of their choosing. Other mashupcampers then vote with their feet to attend. The result, you get a group of between 10 and 30, some times more to turn up and participate. Within a session if it turns out it does not match your expectations you can up and leave.
However, each session is full of information and the self organization extends to the participation within each session. Often, notes a posted live the WIKI so the knowledge created is captured.
Unconferences work because of the openness and willingness of each camper to participate. Hopefully one is happening near you, you should attend.