Just What I Want! Rated 4 out of 5 stars
This is the first extension I have found that does exactly what I want. It works well in Firefox 2, allows me to fill out a whole form with just one button click (or Alt+J key press), and doesn't require any additional programs or toolbars.
I tried signing up for del.icio.us, Digg, MSN Hotmail, Myspace, and Yahoo. The basics worked on every site except Hotmail, and I was able to add rules for the rest. (To do this required basic programming knowledge, but when every programmer sends their rules to the original author, this will quickly work even better.)
Well done and thank you!