FOSDEM is the biggest free and non-commercial event organized by and for the community. Its goal is to provide Free and Open Source developers a place to meet.
This year's event is on 4th and 5th February at at the ULB Campus Solbosch, Brussels, Belgium. Registration is not necessary.
Details are at http://fosdem.org/2012/. There is also a the mailing list.
Subscribe to this calendar