The Sustainable Business Network will be holding its annual Social Venture Institute in November and a few volunteers are still needed. The dates are November 20-21 (yes, it's at the same time as Greenbuild) and volunteers would be required to commit to either one full day or to the entire two day conference. Volunteers can expect to work for half the time and attend talks and sessions for the other half (whether its one or two days).
This is a good local alternative (free) for those not attending Greenbuild. There are only a handful of spots left, so let me know ASAP if you're interested - I'm meeting with the director on Friday.