Yahoo released the latest version of its open-source User Interface Library, a set of components and client-side infrastructure for building highly usable Ajax applications. The latest release includes six new components, as well as a skinning infrastructure that can be used by all YUI components. In addition, the 2.3 release includes over 250 enhancements and bug fixes.

The new components include:

• Rich Text Editor

  Cross-browser support has always been a major challenge for RTEs, and we think you’ll be impressed with how well this editor works across the various environments. You can instantiate it with just a few lines of code for simple implementations...

• Base CSS

  Reset CSS neutralizes browser CSS treatments; the new Base CSS applies some consistent and common style treatments that many developers use as a foundation; Fonts CSS provides a foundation for typography; and Grids CSS delivers CSS-driven wireframes for thousands of potential page designs.

• ImageLoader Utility

  [This component] allows you to defer the loading of some images to speed initial rendering time on your pages. If you suspect that you’re serving a lot of images that are never actually seen by your users, you’ll want to check out ... this clever utility.

• YUILoader Utility

  [This component provides] a mechanism for loading YUI components (and/or your own custom components) on the page via client-side script. YUILoader knows all about YUI’s dependency tree and introduces into the page only those files that are needed to support your desired components.

• Color Picker Control

  The Color Picker provides a powerful UI widget for color selection, featuring HSV, RGB, and Hex input/output and a web-safe color-selection swatch.

• YUI Test Utility

  YUI Test introduces a flexible unit-testing framework for the YUI ecosystem and serves as the foundation for our own unit-test battery.

YUI 2.3 also provides a skinning infrastructure that can be used on all YUI components:

With 2.3.0 we’ve moved to a more formal skinning approach that helps to separate core CSS definitions from purely presentational ones. YUI’s support for skinning makes it easier for you to implement your own design on top of, say, the TabView Control—and it makes it easier to share that skin with others in the community.

What do you think of YUI as a foundation for building rich-client applications?