ShouldIChangeMyPassword.com has a lookup form where you can enter your email address to see if it was in one of the databases with login info that has been compromised and released to the public.
LulzSec and other groups have been hacking an assortment of prominent organisations. Forgood or for bad, they have also been publishing their databases, which typically include emails and passwords. Given that most people re-use their passwords, this site allows the average person to check if their password(s) may have been compromised and need to be changed.
via New York Times
