Yahoo released two cool pieces of code yesterday. The Yahoo UI Blog announanced the release of a AJAX UI library and also a UI design patterns library.
If I get a chance I want to look at the drag and drop code as well as the DOM tools. I hope it's well documented! One of the "hidden costs" of free software is that often times you have to figure it out yourself because of a dirth of up-to-date documentation.
It's nice to see some of these technologies taking off now that we have crossed some major browser adoption milestones for CSS capable browsers. It's a fun time to be a developer.