This is so great for directory submissions it makes it so easy! Using the Firefox Form Autofill add-on is so easy, and there is a tutorial on how to configure it to PHPLD here. And once it is configured you can use the PHPLD Directory list here or the Free Directory List here to make submitting even easier again!
What about if you are SEO and working for multiple clients? Is it possible to fill up the directory submission forms through Firefox Form Autofill? I would suggest ROBOFORM as it allows you to create multiple profile and add alias for submission forms. All you have to do is to click on the client's name from drop down list to fill up the submission form. It has an option "fill" and "fill and submit" Search for "roboform" and you will find the website.
Yes, with this you can create multiple profiles for different clients details, and you can switch them with one click!