Customizing Admin Bar Log-In

Hi, I would like to try my hand at customizing the login in the admin bar, doing something like this:

http://aext.net/2009/08/perfect-sign-in-dropdown-box-likes-twitter-with-jquery/

Actually, since I'm not very experienced in jquery or php or anything, I'll probably try my best to follow that exactly. So I ask, where would I go about putting the html code so that the sign-in thing shows up in the admin bar?