From their site:
The 22nd Chaos Communication Congress (22C3) is a four-day conference on technology, society and utopia. The Congress offers lectures and workshops on a multitude of topics including (but not limited to) information technology, IT-security, internet, cryptography and generally a critical-creative attitude towards technology and the discussion about the effects of technological advances on society.
The Chaos Communication Congress is the annual congress of the Chaos Computer Club (CCC). The Congress has established itself as the "European Hacker Conference" bringing in people from all over Europe and even further away.
The congress will take place in Berlin, Germany from December 27th to 30th, 2005 (four days this time!).
Go there if you can — this is not something you should miss.
(via Hendrik Scholz)