I use about four. I've got the same one for all the sites that demand a password, but I'm not worried about other people logging on as me. Then others for forums, email and bank.
None of the passwords I use are easily guessable. The one I've been using longest (15 years or so) is a random corruption of a latin name of a fish I used to keep! The others are either random letters, randomly capitalised, or people's unusual names, followed by a number.