Update (September 2011) : Y4Faces has been shuttered. There are far ore capable frameworks already out there and there is little sense in continuing y4faces. I will instead be contributing to other open source JSF implementations. In the meantime, look at http://www.primefaces.org/ for a compelling easy to use rich JSF implementation.
Y4Faces is a collection JSF Tags and libraries to integrate the YUI2 library and JSF 2 Facelets. The focus is to leverage the excellent work done by Yahoo to provide easy to use rich controls for enterprise apps. The focus is to provide enterprise oriented, business-y controls.
Summary: https://sourceforge.net/projects/y4faces/
Blog: http://akshatsharma.com/blog/category/y4faces
Developers
Join this project:
Drop me a mail akshat[at]akshatsharma.com.
Get the source code:
Source code for this project may be available as downloads or through one of the SCM repositories used by the project, as accessible from the project develop page
**Y4Faces was briefly called yfaces, until I realized there was an older project by the same name.