I found this blog by Gregory Herek, from listening to this Radio West episode about being gay and Republican (It has a Utah angle and is a good listen, too). From the blog, I see a 2005 update of the 2000 census figures on same sex households has come out (here in pdf):
This first analysis of 2005 American Community Survey data contains some new insights. The number of same-sex couples increased by 30 percent from counts made in Census 2000. Growth in the number of same-sex couples throughout the Midwest suggests that as acceptance of lesbian and gay couples reaches into America's Heartland, more couples are willing to identify themselves.
Of course the problem is that there is significant under reporting that’s improved with better social climate, and so one can’t conclude a 30% increase in 5 years occurred in actual gays deciding to cohabitate instead of remain in the “care-free” single life. Still, I’m sure it is increasing in reality too, and it’s good news either way.
I remember debating whether or not to self ID our home on the 2000 census. After a while I decided I had to be honest and could risk it. I’m glad more folks are feeling the same.