Yahoo! Developers Network: Cool New Releases

Yahoo! Developers Network has just released some cool new API and Libraries. Yahoo! User Interface Library: a set of utilities and controls, written in JavaScript, for building richly interactive web applications using techniques such as DOM scripting, HTML and AJAX and Yahoo! Design Pattern Library: Yahoo!'s own monthly publication on design patterns.
If you've never been to Yahoo! Developers Network before, this site is a repository for APIs, libraries, RSS feeds, plugins, tools, etc. It's also home to the newly acquired properties API like: Flickr, Widgets, Upcoming.org, Webjay. The sheer amount of APIs you can develop on makes Google's API page looks like a startup company, imho.