MIT's Scratch, developed by the institution's Lifelong Kindergarten group, recently underwent an overhaul, with the wraps taken off the new version a few days ago. The visual programming tool is designed to teach children how to code, but there's nothing stopping anyone from giving it a crack.
Scratch itself is a Flash application, so there's nothing to download -- it runs right in your browser. I couldn't get it working in Chrome, but Internet Explorer 10 under Windows 7 had no issues. Once loaded, constructing programs involves moving logic "blocks" from a centre palette onto the right-hand workspace. These blocks have configurable parameters and can be connected together much like puzzle pieces, to create strings of actions. A preview window on the left-hand side lets you preview your progress.
The end result, as you can see from the image to the right, resembles the structure of code you might see in any traditional source file -- if a little more graphical. Programs can be saved and published to the site and users can view the source of any project, making it easier to figure out how certain effects are accomplished.
It's not the sort of thing you'll use for a major undertaking, but it could be the perfect tool to create interactive presentations or prototypes that can be quickly shared online. There's even the potential to use it as a collaboration tool, trying out ideas or conveying information better than what a static online whiteboard can.