The guys over at Clarity Consulting (Kevin Marshall in particular) had such a fun time putting on the recent Facebook Developer Garage that they have decided to hold another event, this time specifically around Silverlight. This is going to be an unconference style event modeled after a barcamp (with the exception that it is going to be focused on one technology). The SilverlightDevCamp Wiki is even being hosted on the Barcamp.org site. As an unconference event, they are looking for people in the community to step up and help out with the event, you can contact the organizers to volunteer or you can go add to the Wiki. They have also setup a Twitter account to use as part of the event.
There is another SilverlightDevCamp in San Francisco 2 weeks ahead of the one in Chicago.