From 27C3 public wiki
HACKBUS
We are travelling by coach, offered by deinbus. Price: 82€ two-way-ticket. Planed start is 12/26/2010 at 12 A.M. at the trainstation in Frankfurt, arrival is ~8 P.M.@ BCC. Planed departure is 12/31/2010 at 1 P.M. @ BCC.
-if 30 seats are sold until 12/18/2010- the coach leaves Frankfurt scheduled.
Go ahead an order your ticket at the "deinbus.de" website.
Frankfurt>Berlin
Berlin>Frankfurt