Statistics for Good!
Practically everyone else has already posted this, but I'm going to jump on the bandwagon anyway (thanks April, for sending the link!).
I thoroughly enjoy the folks at okcupid to begin with - they run a free dating site that doesn't totally suck (at least, for major cities) and has just the right amount of tongue-in-cheekness (in my opinion). Plus, they use their treasure-trove of voluntarily-provided, somewhat-private information to run neat statistical analyses. Like this one, using 4 million match searches to show that no, homosexuals aren't out to seduce heterosexuals (0.6% of gay men and 0.1% of lesbians ever searched for straight matches), nor are they particularly promiscuous (same median reported number of sex partners for self-reported straight and gay men and women). Lots of other good stuff at the link, including a map of who is gay curious in the US and Canada and this excellent bit of advice "I found that a fun game to play with stuff like this is to replace the words 'homosexual' and 'gay' with 'politician'—then you have something that's actually true."