Heh, I recently blogged about a system I came up with to manage this, using a ruby password generator that was linked on HN and storing the results in a dropbox directory. Super super insecure but kinda fun to think through. http://digg.com/u19L9

I don't actually use that system though, I generally use the same user id and generate the password using a formula based on the website I'm registering at and other mysterious factors.