I agree, it is better to have some sort of physical record for registrations and such, then to totally rely on your computer for saving the information. I can't stress this enough to people that I help with computer issues.
Personally, I printed out some simple charts, consisting of four columns and about 30 rows on each page, in which I enter data such as the WebSite, Username, Password and eMail address used. I also print out a copy of the confirmation eMail I recieve from each registration, and place it in the same binder along with my charts with the registration entries. This suggestion might be a bit overkill, but it is how I keep organized.
I started using a binder instead of a notepad because my wife and daughter would occasionally grab it while using the phone, and either scribble, color and basically deface it. Because of this, I went and bought a "Hot Pink" 3 ring binder, and a hole punch, and it hasn't been touched since.
I have a friend that takes a screenshot of confirmation pages for each site that shows the information, and fits as many of the screenshots as possible on to a sheet of paper, and prints them out. It actually works out pretty nice, but each to his own, as I will probobly continue my method