If you have never heard of FOSDEM, it’s the “Free and Open Source Software Developers’ European Meeting” which is held in Brussels in February each year. It usually attracts several thousand geeks from across Europe for two days of presentations and project developer meetings.
I went last year and was really impressed with the “buzz” around the place, it was great to have so many like-minded people around who were all involved with or interested in Free and Open Source projects. As well as the main talk track it has a lot of separate “developer rooms” which are used to host talks for specific projects (e.g. Debian, KDE, mozilla). I attended some good talks, particularly on CMake which was very useful for the LCFG buildtools. I’m going again this year and I am really looking forwards to it, there’s an excellent line-up of talks.