I found a really interesting article at A List Apart dot com about dynamic stylsheet changes using a simple javascript and storing the information as a cookie. I was really itching to try it out with all the talk in the WordPress Forums about retro stylesheets for WordPress. Check out the switcher at http://dinki.mine.nu/weblog/ On the top right hand side of the menu you will see the themes I have installed for my version of WordPress, albeit with a few modifications to suit my second menu column. Feel free to play around and see which one you like best. If you would like to implement this on your site ( no matter which CMS you use, this will work for you ) simply visit the List Apart link above, download the javascript and follow the instructions. If you are confused, feel free to email me and I will try to help.
PS: once you choose a templte/style, a cookie is set on your computer which remembers your choice for the next time 
The themes break in Mozilla (for now) and do not degrade well, but thats not the point of this exercise
this is a test
this is a test