e.g. password to facebook would be:
facebook.com$293MyPasswordYouKnowIt!!123
password to gmail would be
mail.google.com$113MyPasswordYouKnowIt!!123
only annoying thing is that the passwords are long. I guess it's secure, though.
edit: see child post for clarification. I do something above for spammy sites, but for something like gmail I probably wouldn't do that.