The news out of Yahoo! this morning is that they have released their User Interface Library which inluces a set of utilities and controls, written in JavaScript under a BSD license and their Design Pattern Library under a Creative Commons license. On top of that, they also have started up the Yahoo! User Interface Blog to evangelize both releases. A cursory look shows that some of these tools are right out of the new Yahoo! Email beta and Yahoo! Maps beta (as well as some of the My Yahoo! interface).

Yahoo! Design Patterns