I "register/sign up" for 100's of services/products a year and at this point do not know who or where they are. I think it would be amazing to have a dashboard of every place I've ever logged into. Similar to the "app settings" page on Facebook/Twitter
http://www.facebook.com/settings/?tab=applications
Short of a password manager (1password etc), I don't believe this service exists, and certainly not one that automates logging in to 1000's of websites on your behalf.