Got a lot of passwords? Want a secure way to keep track of them? You could buy one called 1Password for $40 or you can use a utility on your Mac called Keychain. Your Keychain (inside your Utilities folder, which is Applications folder) already keeps track of many of your system passwords but it also has a feature called Secure Notes where you can type something (like a password) and then password protect it.
You could put all of your vital passwords on a secure note and then keep it safe with your master password. Not a bad use for the utility. If you haven't taken a look at Keychain open it up and take a look.
Another tip: You can add Keychain to your Task Bar by opening Keychain's Preferences. Inside check the box that says "Show Status in Menu Bar". Now it's even easier to get your passwords.
Update: If you want to see your current passwords that you have saved in Firefox then go to Firefox > Preferences. Click on the Security tab and then the 'Saved Passwords' button. In Safari they are stored in Keychain. Applications > Utilities > Keychain. If you're using Chrome they're stored in Keychain Access.