Make your plans to be there now – FREE. The Association Social Media Unconference is going to be held on Tuesday, June 5 at ASAE & The Center's Marriott Learning Complex located in the Ronald Reagan Building in Washington, DC. There is going to be a great set of topics and lots of attendees – sign up today (simply edit the wiki to include your information)!
Read Dave Winer's "What is an unconference?". This will give you a good idea of how an unconference is structured and what you can expect regarding the format. The key element of an unconference is user's actively participate in the conference.