a) You rock!
b) I was able to modify your script to create a category tag cloud without category archiving. check it out in action here: http://www.mig81.com/index.php?page=zeitgeist
The code is here: http://www.mig81.com/temp/zeitgeist.phps
I know this might seem like a work-around, but some people might be able to use this sort of solution.
c) Is there a way to adjust the *increment* at which the text size is adjusted? Some of the text is too small…
d) You rock! Keep up the good work!