I use a password manager on my iPhone (I use Codebook, by Zetetic), and it allows me to hold numerous passwords/logins/emails/PINs/account numbers (sorted under categories of my choosing, like "travel", "work", "financial") - all under a single password. THAT password is a weird one like it's supposed to be, with a few lower case, a few upper case, a few numbers, and a few symbols (and not a word in any language). That way I can look up different passwords or PIN numbers as I need them.

The program can even generate random passwords if you want it to -- I don't. I use variations of a theme for most everyday passwords (like shopping sites or frequent-user cards), but I know I can easily change a password any time I want or need to, and I can always look up the new one on my iPhone if I forget it. It's particularly helpful for the ones I don't want to use that variation on a theme (like banking), and for passwords I use rarely.