Masturbation
I was doing some casual browsing yesterday and came across a couple of interesting sites on masturbation. The first one, http://www.mymasturbation.com/, describes itself as "Masturbation Stories from One Thousand Real People." Pretty interesting reading; it includes short posts from hundreds of people, both male and female, on how they masturbate. The second one is similar, with some occasional humorous comments added by the webmaster: http://www.letsmasturbate.com/.