BugMeNotBugMeNot is a database of usernames and passwords for websites that force you to register. If you encounter one of these websites, visit bugmenot.com and plug the address of the website into the box. Use one of the username and password combos to log in. If they no longer work, you can help by registering your own disposable account (see below) and adding it to the BugMeNot site.
You can integrate BugMeNot into your browser, if you like. Just install the Firefox add-on, Chrome extension, or add the bookmarklet from the BugMeNot website.