I don't use the same password for every website, but I do use slight permutations. (For example, adding extra numbers or letters onto the end of a longer random letter and number root password that I have memorized.)

Of course this is probably not the best technique, but its probably secure enough. In addition, I do use alternate passwords for sites that I don't trust. So, for example, I would never use a permutation of my email password for a random site on the internet.