Keychain is a fabulous application which comes as standard on every Mac. It is the program which stores all your passwords for you.
For me, it has proven to be a lifesaver time and time again. I have more passwords for more sites than I have hairs on my head (not that that’d be very difficult!). I have systems in place to try to help me remember passwords but I frequently find myself staring at the login screen of a website with no idea what password (or username) I chose for the site.
This is where Keychain comes into its own. Launch it from Applications -> Utilities, search for the website, click the Show Password tick box. You are prompted to enter your login ID for your Mac, on doing so successfully, your password appears – brilliant!