Konfabulator [via RAILhead design] is the coolest Mac OS X app I've seen in a long while. It's a manager for those tiny desktop widgets that everyone uses - calendar, battery monitor, weather - and these downloadable widgets look beautiful. Full use of the OS X transparency and shading. The app itself is polished to the extreme. Drag and drop installation, and the first time you run it it explains what it does and how to use it. All apps should be this easy.

And here's the kicker. Konfabulator is fully open to developers -- and widgets look trivial to write. Each is an XML document that says what images go where, and what to do when there's an event (mouse click, mouse over, etc). It's all in Javascript, which makes things really easy, especially because you can also fire off AppleScript, shell commands and make connections over the www. One of the guys behind it is Arlo Rose, who was also partially behind Kaleidoscope on Mac Classic, the skinning engine that had an enormous community developing themes. He obviously wants to do the same here. And I can really see it happening. Tiny, lightweight widgets that look gorgeous and do powerful things.

Documentation is in the Widget Workshop (and it's comprehensive), or you can Show Package Contents of any widget to read the source. Their journal also gives you an idea about what the developers are thinking. This is very definitely one to watch.