www.open-personals.com
Based around drupal 4.7, A new, free, dating site with ideology was just launched!
A feature I have yet to see in any other dating site is the multiple-communities and questionnaires structure, allowing users to directly influence on what they can search for. There are other dating sites allowing users to submit their own questionnaires, but the result is usually a million questionnaires, that each one is taken by a fraction of the other site's users.
Open-personals.com is build differently: The web is full of online communities, that gathered around a certain subject, lifestyle, etc. Open-personals is inviting these communities to define, along with the site's team, a custom questionnaire - for all users to take - if they like. Four of the questions are searchable, so you can look for somebody that answerd "x" to question "y" in questionnaire "z".
The idea is, of course, to include as many communities as possible, but even then it will still be a managable number of questionnaires - for users to take - search - and be found by other users,
Though this dating site is not "open-source" by definition, and the code is not available, it is by nature inspired by the open source idea. It is free, and it is based on the internet community for development and support.
Feel free to drop in. Feel free-er to sign up. And more than that - to assist. There are hips of things to do!