I would like to use javascript to develop general-purpose GUI applications. Initially these are to run on Windows, but I would like them to ultimately be cross-platform.
You could try to combine something like SUN's Lively Kernel with Mozilla's Prism.
Lively Kernel is a GUI Stack written entirely in JavaScript using SVG for display purposes.
Prism is a way to launch web applications without showing the browser in which they run.
Very bleeding edge though, use at your own risk. :-)