IPCO (Integer Programming and Combinatorial Optimization) is held in the summer, and can occasionally overlap with SoCG. I've been in touch with Friedrich Eisenbrand (organizer of IPCO 2010 in Lausanne) and it looks like the two conferences will be back-to-back and disjoint in case there are people who wish to attend both. Thanks to Friedrich for moving IPCO to earlier in June (9-11) to make this happen.
In even more important news, the Zion Curtain is soon to come down in Utah. All this means for visitors is that you won't have to pretend to become a member of a 'private club' to drink at a bar in Utah any more.