The dating site OKCupid maintains a blog about the data they collect from their users. OKTrends has some extremely entertaining posts, and they all happen to be about statistics. The site has data from 100 times the number of people polled for nation-wide Gallup poles (300k people v. 3000 people).
Commenters point out that, as opposed Gallup polling random people, OKCupid polls only members. The people who are members of OKCupid could be very different than the people who are not. Still, it's a lot of data and it's interesting to see differences between people by state and gender. For example; the length of a introductory message and the chance of a response, how different religions and races interact on the site.
I found the site through a post on BoingBoing. The interesting part of the post was how men and women respond to attractiveness. Men gave a fairly even bell-curve to the female attractiveness on the site. Men replied more often as the attractiveness of the woman increases, until the woman was so attractive that messages dropped off. This is about what I'd expect. Guys like attractive women and many guys would feel they had no chance with the extremely attractive memebers, so they wouldn't even try.
Woman, however, were different. The women on the site found very few males on the site to be attractive (rating 80% below average in looks) and tended to message the slightly below average men the most.
The discussion on the BoingBoing post and the original post by OKTrends are both worth reading if you are interested. There is a lot of discussion about why women found so many of the men below average in looks. An important part of that discussion has to do with how OKCupid works. I don't understand it fully, I'm not a member, but from what I read in the comments there is a system that automatically alerts a person if you rate them at a certain level and above. The commenters suggested that women are intentionally not selecting higher levels to avoid unwanted contact from the men they are rating. Another commenter complained that they system "baits and switches" when you are rated high by someone, by showing other profiles with the one person that thought you were attractive. The woman said she rates all of those people as" unattractive" in protest of this feature.