Soul Mate Find is geared toward people who are trying to find life partners.While using the site is free, it does require "credits" which you earn by logging in every day or by referring friends to the site.
Users can take over a dozen quizzes and answer hundreds of questions on everything from whether or not they believe in love at first sight, to questions about values and morals, to really narrow down their matches.
Casual Kiss is, as the name implies, for those who are looking for something casual.
This site also has a mobile app available for free.
Plenty of Fish works to set you up with other members you're likely to be compatible with based on a chemistry test.
You'll also get free relationship coaching via blogs and a popular message board.
This site is for people looking for dates and also for casual flings. Date is another one that uses an algorithm to match users.