Online dating: friend or foe?

The U.S. online dating market is expected to increase spending to over $900 million in 2011. Here's a quick peek at the most popular websites for finding that special someone...or a night of no-strings sex.

Compatible Partners: Matches men and women with compatible singles of the same sex, taking into consideration what it considers key dimensions of personality. A comprehensive questionnaire is given before the user browses the website. Compatible Partners was launched by eharmony Inc. on March 31, 2009, following a lawsuit against eHarmony for discrimination against same-sex couples.

Grindr: 1 million members. A networking application for the iPhone, iPad and iPod touch. Available for download from the Apple application store, Grindr comes in both free and subscription-based versions. The app makes use of the device geolocation, which allows users to access other gay and lesbian men within close proximity. Beware of stalkers.

MANHUNT: 4 million members, including 1 million in the United States. Owned by Online Buddies, Inc., Manhunt facilitates same-sex introductions. Some profiles are of a non-sexual nature and explicitly state that they are not cruising for sex. The majority, though, are sexually explicit and include nude photographs and graphic language. 

Match.com: 20 million members, with a 49:51 male/female ratio, and websites serving 25 countries in more than 8 different languages. Though no statistics are available regarding same-sex matches, separate tabs are available for searching M4M or W4W.

OKCupid: 3.5 million members. Free dating and social networking website which features member-created quizzes and supports various modes of communication: personal blogs, public forums, instant messages, emails, and "winks."

Plenty of Fish: 11 million members. popular primarily in Canada, the UK, Australia and the United States. The service, based in Canada, is free to use and allows you to set up your own free dating profileand then find matches based on a set of compatibility questions you answer. You can also choose to simply browse based on zip code, religious preference, ethnic background and several other preferences.

Craigslist Personals: 50 million viewers monthly. The Craiglist Personals pages appear as a section under each regional or city site of Craigslist. Caigslist Personals is subdivided into several sections, ranging from the "Strictly Platonic" to "Casual Encounters."