BugMeNot is dedicated for sharing website logins. Basically anyone can submit their own user account of a particular website and password, and let others use it.
I found it very useful sometimes! For example, there are lots of websites that limits theirs features just because you are not logged in. And for signing up (registering), sometimes you need to give out your e-mail address, personal information etc. which is very time consuming (and not fun at all!). Not to mention sites that force you to pay before registering!
Their database of passwords is decent IMO, I found an account I need for a website (Rootkit) and the password works (despite the votes at BugMeNot which marks near 20% login failure). Everybody can contribute to the database! Just make sure you are not bugged by people using your passwords.