I have a pretty elaborate password scheme/system I've devised. It's fairly elaborate and if I explained to you how it works you could guess my password anywhere once you know one password. Without the explanation, knowing even a few passwords won't help you.
What bugs me is that each site has different rules for passwords and far as length, allowed characters (i.e. can I use @#$% etc.), required characters and so on. Most sites don't even post the rules (using a JavaScript hover-over bubble or something) near the password box.