Very quickly (because twice in one day is probably more blogging than absolutely necessary), I've seen three or four posts this morning about having to remember yet another username and password for the various Web 2.0 accounts.
There are two approaches to this. The first is to have them written down in a notebook. Yes, I know that sounds crazy, but most hackings happen remotely, so whoever's trying to get into your computer is unlikely to also have access to your notebook. It's not foolproof, but for non-essential accounts (like the Web 2.0 ones), it can be handy. You don't even have to write down the whole password, just the equivalent of a security question to jog your memory each time.
The other approach is to use something like KeePass (assuming you can get past the spelling). It acts as a secure database for all your passwords, so you only have to remember one, super-strong password instead of lots of different ones. You can even set it so that it has to have a physical key as well - ie, you have to plug in a USB drive with the key file on it and enter your password in order to get access. You can install it on any computer, and it's about as secure as you can get.
It also frees up your memory, and allows you to use multiple passwords without worrying about forgetting them. Now, all I have to do is remember what passwords I used in the first place so I can put them in my KeePass account...