If you've always been interested in Open Source / Free Software GSM using OpenBTS, you might be interested in the upcoming three-day OpenBTS workshop in Pfarrkirchen/Germany.
The workshop is held by OpenBTS project leader David Burgess, and will cover subjects ranging from OpenBTS installation, configuration and deployment down to actually extending OpenBTS with some custom code.
p.s.: Please don't misunderstand, the workshop really is about OpenBTS not OpenBSC - though there might be OpenBSC folks hanging around ;)