That would be very much of interest, Ian.  One potential issue, though:
 The table of contents generated by org-mode uses just one <div></div>,
with nested <ul><li> elements.

I spent a few hours tinkering with variations on the jQuery approach at
http://www.sitepoint.com/forums/showthread.php?822342-JavaScript-list-of-links-with-sub-lists-hide-and-show,
with code at http://jsfiddle.net/GeekyJohn/9kaQQ/.  It initially
looked promising, but I haven't been able to make it reliably play well
with having links in the TOC headings.  Of course, when it comes to jQuery
I'm not much better than a cargo-cult programmer.

Thanks,

--D. C.