Here is the info on how to create themes for developers
http://code.google.com/apis/themes/docs/dev_guide.html
need knowledge of html, css, a little xml, and image manipulation skills...
I have all but the last, but the last is what makes it look cool !
Just as backinfo, iGoogle is Google's personalizable portal for users of gmail, Google calendar, and many other custom pluggable objects...u get to it by going to
www.google.com/ig login using ur gmail/google account username etc...