Ahh... Eric, sorry, I misunderstood your question...
www.sprint.com(Javascript must be enabled, by the way, so if you're using NoScript...)
If you look at this page, on the right side there is a combo-box (select-box) from which you choose an Account Type, ie, MyNextel; My PCS Wireless; Sprint Personal Long Distance; etc... when I select one of these, the Username and password are indeed populated, but the first field is not... and I'm not sure if this will work as expected, since the username and password fields don't show up until you make a choice.