BugMeNot.com

Don't want to register at the 50th website (say, www.podunk_little_newspaper.com) that's asked you to provide personal information? Go to this website, put in the URL and they'll check their database. If they don't have a registration on file, fill a fake one out for them and submit it to help their database grow.
BugMeNot.com: "Bypass Compulsory Web Registration"