On April 17th and 18th the German OpenData Network will organize a BarCamp around Open Data in collaboration with Hack de Overheid from the Netherlands. The event takes place in Berlin.
More info in the wiki page: http://wiki.opendata-network.org/index.php?title=Hack_the_Government
Or e-mail info [aet] opendata-network.org
Announcement of the event in German.
A BarCamp (explanation) around open data, with the motto 'all you ever wanted to do with open government data, but never dared to ask' Held in Paris, December 12th 2009. More info in French
Hack de Overheid ('hack the government') is a one day event that brings civil servants together with coders to discuss Open Data issues, as well as build applications during the day.