Free unconference with (supposedly) free beer afterwards. It's a bit more focused than the BarCamp Chicago that's on August 15, with a focus on social networks and communities. You can sign up just by adding your name to the wiki - it would be nice if you did it in alpha order, rather than just at the end as some people did (cough ColonelTribune cough).

(Disclosure: Dawdle.com is a sponsor)