Windows 7 Tip: 
Autofill Forms is a new Firefox addon which will help you to fill out web forms automatically based on the profiles you create. This one is my one of the best extension. Its very simple to use. You are able to edit, remove, enable/disable the provided rules and to add your own ones. You can configure the order in which the rules are to be applied and define site specific rules.
Profiles can be used to switch between several sets of rules. Autofill Forms only becomes active for the moment it autofills forms – so it doesn’t use any system resources while surfing. To protect your personal data you have the option to store the form field rules encrypted.
I think I’m content with Google Toolbar. It has an autofill feature that does the job pretty well.
cool. i guess this will be very useful to fill the profile pages in various networks :p
I am with Google Toolbar
I too use Google Toolbar to fill out details.
i have posted a some what similar article if u like have a look.
http://www.technixupdate.com/auto-fill-up-the-comments-form-section-in-the-wordpress-blogs-automatically-to-comment-better-and-faster/