From www.fosdem.org/2010/

FOSDEM is a free and non-commercial event organized by the community for the community. The goal is to provide Free Software and Open Source developers and communities a place to meet to:

• get in touch with other developers and projects;
• be informed about the latest developments in the Free Software and Open Source world;
• attend interesting talks and presentations held in large conference rooms by Free Software and Open Source project leaders and committers on various topics; and
• to promote the development and the benefits of Free Software and Open Source solutions.

Participation and attendance is totally free, though the organization gratefully accepts donationals and sponsorships.