I use one simple, probably easy-to-guess password for all those annoying sites that demand an e-mail address and login password. The e-mail address is the name of the annoying site @ my domain.
Mail to any unknown address at my domain is automatically forwarded to my Spamcop account (which gets a stunning amount of mail every day). Those few that aren't spam are forwarded to me.
The important stuff (PayPay, Ebay, banks, etc) all have unique and hard-to-guess passwords. I keep them all in my iPaq - and have to look them up all too often.