BarCamps are user structured conferences.
From WikiPedia http://en.wikipedia.org/wiki/BarCamp:
The name "BarCamp" is a playful allusion to the event's origins, with reference to the hacker slang term, foobar: BarCamp arose as a spin-off of Foo Camp, an annual invitation-only participant driven conference hosted by open source publishing luminary Tim O'Reilly.