Casual Kiss is, as the name implies, for those who are looking for something casual.
You can also view the site in Spanish or Portuguese, which may be helpful if you are bilingual.
However, if you only have a few minutes, it can be a good starting point.
The profiles on Mingle2 are pretty brief, but one advantage is that it allows you to search for people by interest.
It has social networking aspects such as a blog and an add a friend feature. OKCupid allows users to create an individual matching system in order to find the most compatible singles.
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.