NESEA's 2009 Green Buildings Open House will return the first Saturday in October, which falls on the 3d this year, and I highly recommend it. Last year, G. and I went out to western Mass. and toured five or six great places, and then had the chance to follow up with a couple of other places on a second trip. A lot is happening out there.
According to Mary Biddle of NESEA, the New England Sustainable Energy Association, "This is the largest renewable energy event in the country, operating in conjunction with the ASES National Solar Tour. The estimate last year was that over 100,000 people across the United States participated in the National Solar Tour," upwards of 15,000 of them via NESEA's end of it.
If you have a building to put on the roster, registration is open into next month. If you're just interested in seeing what your neighbors are doing, you can see what's available near you at this link: nesea.org/greenbuildings. Please note, it's a dynamic listing, so it will fill up as time elapses.