About running an event in this style
The folks at O'Rielly (yes, the publishing people) were kind enough to turn us on to this style of event. We call it a "Summer Camp", because we run these once each summer. But call it a "Bar" camp, "Foo" camp, an "Unconference", or whatever, there are some common elements to this style of event and lots advice available from people who have run these events before.
Below is some information O'Rielly sent us that got us started. Many of these links lead to other links which will keep you busy reading for quite a while.