Married but Lonely is a site specifically for people seeking extra marital relationships. Registration is discreet, secure and basic access is free. You can also join the site for a 3-day free trial membership, but you must provide a credit card number to do so.
Married But Lonely is a niche dating site aimed at those who are married but looking for a relationship outside the marriage. The site has been online since 2003 and has nearly 70,000 members. It serves the US, South America and Europe. No matter what you're looking for, you can likely find it here. As you might imagine, many members are looking for no strings sex, but some people are interested in long term mistresses or companions. Most of the members on the site are male, so women will definitely have lots of partners to choose from.
Basic services are available on the site, and include messaging, advanced searches, checking who's online, and group chatrooms. Private chat is available to paying members. The picture rating tool is fun, and allows you to quickly view a large number of photos and express interest (or lack of). There's also a selection of adult movies available to subscribers.
You can join the site with a three day free trial membership, but you must provide a credit card number to do so. During the free trial, you will be able to browse the profiles of other members. Keep in mind, however, that many people do not put much info in their profiles, in the interest of discretion. Those signing up should be aware that the trial will automatically upgrade to full membership unless cancelled. The unsubscribe (cancel account) button is located on the account preferences/info page.