I do like coffee-script. Basically, it's JavaScript, but properly defined.
I'm pretty sure that this would be 1/ no pain for JS users to use 2/ a lot more attractive
On the other hand, you are likely not to be able to use all previous JS libraries…
More at : http://jashkenas.github.com/coffee-script/
P!
Another approach would be to use OMeta (http://tinlizzie.org/ometa/), for which there is a Scheme version (http://www.lshift.net/blog/2008/07/01/ometa-for-scheme). The OMeta project includes a parser for JavaScript (http://www.tinlizzie.org/ometa-js/#JavaScript_Compiler) which basically produces S-expression based ASTs.