Open Source RIA Framework For .NET: LiveUI

LiveUI is a powerful, flexible & open source rich internet application framework for .NET.

It has a modular system which allows sharing .ascx user controls & resources between ASP.NET web applications.

Working with JavaScript from ASP.NET applications becomes simple as the framework includes tools for JavaScript generation, caching, dependency management & more.

LiveUI has an Extjs.Controls module which includes ASP.NET wrappers for all ExtJS components making usage of them so easy inside ASP.NET pages.

Also, there is a built-in solution for URL parsing & generation which means creating user friendly URLs is not a problem with the framework.