280North’s Atlas looks pretty amazing, a tool to create web applications (Rich Internet Apps) but not based on Flash / Flex but on the core HTML, CSS, Javascript capabilities of modern web browsers.
Built on the open source Cappuccino web framework which has the advantage of abstracting away all the browser quirks etc and just allowing you to focus on creating really powerful web applications.
It uses a programming language called Objective-J which is built on top of Javascript and modelled on Apple’s Objective-C language used in Mac OS X and iPhone OS applications.
Check out the videos below for demos of it in action.