This may not be a new idea, but I use Address Book for more than a contact list. Useful also for other bits and pieces of info. Example: I spent way too long today finding the toner number for my B&W Samsung after using up the starter cartridge. Finally located it and a site selling at a good price, so I made a "card" with the suitable title ("Samsung toner"), the a link to the purchase in the URL field. Entered the purchase date in "Notes" so I know how long it lasted next time around.
"For what is age but youth's full bloom,
A riper, more transcendent youth" - Oliver Wendell Holmes