The PHP Web Toolkit enables the rapid development of multi-layered web applications and is designed to be easy to use, extensible, reliable, reusable, scalable and secure. It integrates with ADOdb, FCKeditor, kses, Libmcrypt, Libmhash and Smarty.
The xWire framework is a toolkit used to build Java web applications, but is flexible enough for other uses. It is ideal for building AJAX apps and consists of both client and server components, each of which can be used independently of the other.
JAST (Javascript Toolkit) is an Open Source cross-platform javascript framework that aid users to perform the most hard operations with few simple lines of code.
It's modularity allow the download only for the code required to the page.