The Washington DC's BarCamp recently held an event, or "unconference" as it is called by attendees. Kim Hart of Wahstington Post wrote an article "Twittering Types Share Ideas Offline" about the event:
Upcoming events below in the Mid-Atlantic region are listed at the BarCamp web site. Participation is open to the public. All you need to do is to follow the link to each event and sign up from there.