Pam Spaulding points to this report (PDF format).  Not surprisingly, San Francisco has the largest gay population in the country (8.2% in the metro area).

But what she (and I) found startling was the increase in same-sex couples from 2000 to 2005:

Seems gays are coming out all over, and not just in New York and California.  North Carolina, for example, showed a 21% increase in out gay couples.