Here is the problem: You constantly hear about don't use the same password on every site. Ok, makes sense, except that a lot of people have login information to 100+ websites. Sure that are tools like keepass or lastpass or whatever, but then you just need to break 1 password to have access to them all
Then you get redicoulous requirements on some websites, like can't use special characters, can't be longer than 10 chars. Why? You should be using a hashing algo which means special characters or max length shouldn't matter (within reason)
I have about 4 passwords
My low security one where I do not give a shit if people hack my account eg slashdot/most forums
Medium security - Password for sites I care a little about and that contain some personal information eg, some forums, some online shopping sites that don't store cc info, etc
High security - Mostly used for sites that are used for purchasing things and that have linked CC info to it
Very High security - Used for financial institutions
This way I always know when I go to a site which password it uses.
However, I have been thinking about changing slightly how I do my passwords... the base password will always stay the same, but I may prepend or append the the first 3 characters of the sites name or something (maybe not quite this obvious). This may increase security of password a little, as well as benefit of most passwords being unique.. but not sure how much it increases the security by