In Berlin, I was chatting with Tim Pritlove about the
annual
Choas Communication Congress which is held in Berlin.
http://en.wikipedia.org/wiki/Chaos_Communication_Congress
This event attracts 2,500 and 3,500 participants (according to
Wikipedia) and a central feature is the "hack center" which gives
access to around 600 people for whatever.
Not described in the Wikipedia article, but attested to by Tim
Pritlove, it's a rocking good time.
I wrote a short English abstract for this site. Feel free to take part
in the discussion (English/German/whatever).
Mathias