Firefox has nice built in password management features, however the one thing it is missing is the ability to export your saved information. Doing so is a nice way to get these entries into a password manager program. To add this ability to Firefox, check out the appropriately named Password Exporter add-on.

This extension allows you to export your saved passwords and disabled login hosts using XML or CSV files that can be imported in another browser or computer.

This is the functionality you would expect: simple and effective. Just make sure you do not keep the export files sitting around as the data is stored in plain text. When you are done with these files, be sure to permanently delete them.