Want to control all of your passwords with a single one? Firefox does have the master password option but now there is also Password Marker X. This cool extension will give you one password to rule them all.
Here is more about Password Marker X from the developers:
If you’re like most people, you have a few passwords that you use over and over again on many different websites. You know this isn’t secure, but you do it anyway. Why? Because it’s difficult to remember a unique password for each and every web site that requires one.
PasswordMaker manages all your online accounts using either new, uncrackable passwords it creates, or your existing passwords. It even automatically populates webforms for one-click login.
Want to learn more? Check this extension out at the Firefox Add-ons website.