To make unique passwords for each site I use a simple formula on the domain name that I can work out in my head and append it to a "master" password. An example formula could be "take the last 2 letters of the domain name and shift them 1 letter forwards".

This means your passwords always have different hashes, which will reduce brute force attacks. Depending on the complexity of your formula and how much time the attacker has, it may not be possible to work out your GMail password from your Sony one.

Another password tip I read was moving your hands up (or right) 1 row when typing. For example, "a" becomes "q". This adds an extra step to creating a dictionary for an attack so should secure your password a bit.