Fleegix.js includes a concise but powerful events system, an industrial-strength XHR library, a simple, no-muss-no-fuss XML parser, and some handy tools for working with Web forms, as well as other basic tools you need to build an Ajaxey Web UI.
It comprises code I've been using in personal projects for quite awhile now, as well as updated versions of some of the code that was included in my Ajax book. The current release is version 0.3.1.
The impetus for building the site was at least in part what PPK of QuirksBlog referred to in a post back in February as "regaining [his] sense of fun." It's been years since I built a site from scratch, and I had the urge to pull up Photoshop and play with some design.
It ended up being really fun doing an over-the-top take on the stereotypical Web 2.0 site -- with the in-your-face gradients everywhere, and the big honking badge thing at the top. It was also a great opportunity to go a bit more in depth into CSS, and approach it from a different angle.
Giorgio: Thanks very much for the bug report. It's fixed now in trunk, and that fix will make it's way into the next bugfix release. Much appreciated. :)