I have successfully implemented alist aparts style sheet switcher using
alternative styleseets.
Link
http://www.alistapart.com/stories/alternate/

I am currently using it to allow visitors to control the color scheme. I'd
like to provide additional controls for changing font size. I've got 4
stylesheets for color scheme, 3 for font size. I can't figure out how to set it
up so that there is one "group" of stylesheets being switched for colors and
another being switched for fonts. I need them to work independent of each other.

Any ideas?

Thanks,
Jeremy