From Apple’s page on the topic.

“...there may come a time when you need to have access to your serial number, hardware configuration, passwords, email server or internet access information. And then you discover that you've either forgotten or misplaced this information.”

To make your life a little easier, Apple created this handy cheat sheet to organize often-asked and useful information. The PDF document link below, print it out, fill out the fields with your information, and store it in a safe and secure place to avoid others from finding out your important passwords.

I’m thinking, “this could make a great simple database, so it might be built. contact me if you are interested in my closed test of it.

my_mac_cheat_sheet.pdf

WARNING: I was never a fan of written passwords, open to physical theft, and I will deviate from Apple standards where appropriate to protect the interests of those I support, and recommend password storage that is not open to theft and compromise. Use that piece of advice at your own risk.