I just finished Day 1 of CITCONF here in DFW. It's an openspace style conference focused on the area of continuous integration and testing. Openspace means that all the attendees determine the topics of discussion.
For something that is not a 'vendor based' conference, Citconf seems incredibly well sponsored (food, drinks, swag, etc)
There are some very experienced people attending. It will be interesting to see where the sessions take us.
The organizers have one rule for the conference. It's called "The rule of two feet". Basically, the attendees are responsible for making sure that they are either contributing or receiving value at the sessions they attend. Therefore, if one of those isn't happening, anyone can feel free to get up, walk out, and find something that will be more valuable. I'm excited to see how this rule plays out in practice.