I recently went through and added custom items to the keychain access program. I keep passwords and serial numbers in my Keychain Access program. If I need to look up a password or serial number, I just open keychain access, select the item from the list and the click the show password checkbox. A dialog comes up to authenticate and my password is displayed in plain text. I use this for websites, software, applications serial numbers, instant messengers, etc. So far so good! The good thing about using keychain access is that all of your passwords are kept secure - all you need to view them is your single keychain password. Unfortunately keychain access doesn't automatically fill in the passwords or serials, but it's a great place to stash them. Your keychain is stashed in your ~/Library/Keychains folder (in case you want to back it up). You can create customized keychains, etc.