I just run into this interesting project by the people that did Firefox, take a look at it:
http://labs.mozilla.com/2007/10/prism/
Right now, it’s pretty basic, other than save a few seconds to pop up a browser, and being able to alt-tab to it and being completely clean (without browser toolbars, etc) , i don't see much benefit, but, the idea of making web apps function more like desktop apps is pretty cool.
I haven’t fully tested 3dCart in it yet; if any of you want to give it a shot, post here what you think of it.