I'm going to attend the 22C3 in Berlin 27.12-30.12. https://events.ccc.de/congress/2005/wiki/22C3_Public_Wiki
It's not related to Lisp in any way but as both, Lisp and their definition of "Hacker", include "significant affinity to efficiency", I hoped that the intersection of Lisp coders and 22C3 attendees would be non-nil.
I've been to the past four congresses and will be in attendance at this year's congress as well. I never found any other Lisp people there, but never looked very hard :-)