I spent 90 minutes this morning with a company in Utah County (Lindon, actually) called Vultus.  I was pretty impressed.  If they'd shown me that product three years ago when I was building consumer oriented eCommerce tools, I'd have written them a check on the spot.  Its that cool.  Here's what it does:

Vultus has created a Javascript library and professional IDE that allows you to create a think client experience without any client footprint.  Since the Javascript runs in the browser (IEv5 or later, Netscape v7 or later, or Mozilla) lots of interesting things can be done that just aren't possible on a server.  No plug-in is required.  The library is around 300K and is cachable, so its fairly low overhead.  The IDE creates professional looking GUIs with a drag and drop interface. 

One of the cool things they can do it interface to SOAP services.  They have a tool which automatically creates a GUI that runs in the browser from the WSDL. 

They've put together a demo site that shows some of the capabilities.  Be sure to look at the source.