I'm fascinated by the Craigslist man for man personal ads (NSFW). I'm not in the market myself but the discourse is so efficient that I enjoy reading it in idle moments, it's a great capsule of gay casual sex culture. Most of the ads are quite terse: the poster's age, a self-description, a description of the man they're looking for, preferred sexual acts, and a proposed location.
For the past seven months I've been archiving the RSS for the Bay Area boards, a collection of 485,000 unique personal ads. Here's the distribution of ages of posters.
I'm hoping to do more analysis. I'm particularly curious about the relation of the poster's age and the age of their preferred partner, but the data is a bit fuzzy.