FOSDEM (Free and OpenSource Software Developers European Meeting) will happen again in 2006, the last week-end of february in Brussels.
I expect it to be once again one of the best events for developers and other people interested in the internals of the libre software movement.
More details at http://www.fosdem.org/2006/index/news/fosdem.
Update 14/11/2005 : Like last year, the CALIBRE project will host a room to deliver presentations from researchers studying libre software projects from an academic perspective. If you’re insterested in making a presentation, please check our call for participation.