ArbCamp 2008, to be held Thursday December 18, is still open for registration! It had sold out, but they were able to find a larger space and re-open registration. 

See the following note from the organizers:

After selling out in 3 short weeks, and facing the prospect of turning
away 100 waitlisted attendees, we've changed venues to accomodate
everyone!

Thanks to SPARK, we have a new location for ArbCamp on the edge of
campus - Cottage Inn at 512 E William St, Ann Arbor (just a few blocks
from the original SPARK location). Please join us this Thursday at 6
PM, and direct anybody else who might be interested in an evening of
intense speed geeking and community building to register for ArbCamp
08!

 http://a2geeks.org/display/geek/ArbCamp+08