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.