If you don't read TheoryNT (and you should!), you missed the call for participation for
APPROX 2005 + RANDOM 2005
8th. International Workshop on
Approximation Algorithms for Combinatorial Optimization Problems
9th. International Workshop on
Randomization and Computation
22-24 August 2005
As the titles suggest, the two workshops focus on approximation algorithms and randomization. They are not large (accepting 20/21 papers), and are a good place for more focused discussions on these topics.
If you're a researcher in either of these areas, you know about these anyway, but if not, and you happen to be in the Bay Area, you should definitely stop by there.