A couple of weeks ago I tried out the website building tools at www.squarespace.com
I really really impressed with how far you could go in customizing your site's look and feel with a relatively small number of options. And by small I mean somewhere around a thousand. So maybe that's not small, but it is finite. So I started with a list of elements that I'd like my users to be able to style and the ways they would want to style them. Next I added form fields for each style option to my theme-settings.php file and used their output to modify my theme. This was pretty cool, but what I really wanted was to see the changes I making in real time, which is where jQuery and jQuery UI came in handy.
I think the result is pretty compelling and have proposed a session for Drupalcon Paris on the subject. Take a look and let me know what you think.