If you have to create multiple passwords during your day, using a password generator is an easy way to avoid having to think too much! pwgen is such a generator, integrated right into Firefox.
pwgen is really a simple tool. After the usual install and restart of Firefox you will see a P has appeared in the status bar (at the bottom of the browser). Clicking this, and a random password will appear above it, and will have been copied to the clipboard, for easy pasting. If you're not happy with the password, keep clicking the P until you are!
Right clicking lets you into the options menu, where you can set rules for creating passwords, including the character types, length and whether to display or save the password or not.
There is nothing else to it! It doesn't explain how it creates passwords, but they seem completely random. It's more useful for network engineers and System administrators than everyday users, as the passwords are not memorable!
pwgen is a neat, and efficient little add-on for anyone who needs password generation