Why is Google doing this? Because the more powerful web applications become, the more important Google's search, browser and nascent OS become. More relevant to developers than some grand anti-Microsoft conspiracy, though, is that some serious UI sweetness may be forthcoming.

The Closure Compiler will scrunch up your weighty javascript for super-efficient deployment, allowing you to do more in the user's browser with a much smaller code payload to deliver. The compiler is available in binary, as a web app and as an API. Google is also releasing a Firebug extension called Closure Inspector that will translate those compiled bits of code back into their original format.

The Closure Library is a collection of cross-browser, modular, "industrial strength" UI components from across the various Google properties. Rich text editor, DOM inspector, drag and drop ala Google Maps - you want it, you got it.

Also released are a number of high-efficiency Closure Templates.

Google's Amit Agarwal says that all of the above were originally built as "20% time" projects but then became fundamental parts of some of the most popular Google applications. Now these technologies can be used in building your apps, as well.

It will be interesting to see how these Google offerings stack up and get adopted compared to Yahoo's YUI library.

With that in mind, Facebook decided to internally develop a library for creating JavaScript animations in FBJS. "And then we thought: 'why stop there?' The library had very little Facebook-specific code, so we took some time to modularize it, and now we're open-sourcing it for everyone," said Facebook developer Marcel Laverdet.

Facebook is following in the steps of rival web giants Google and Yahoo!, who both have open sourced internal JavaScript libraries. While Facebook's release of the animation library is a far cry from the more complete libraries released by Yahoo! and Google, such as Yahoo!'s YUI or Google's Web Toolkit, it is a step in that direction. Releasing open source development libraries is a very smart thing to do, because it builds capital with developers and attracts developers to your platform. For Yahoo! and Google, their development libraries help to attract developers to their other APIs (such as Google Maps or Flickr). For Facebook, releasing libraries like Animation could help draw more developers toward their platform.

The Animation library is described as a way for developers to create "customizable animations using CSS and DOM manipulation." It is released under a modified BSD license.