ASP.NET, AJAX and JUICE-UI
The most attractive reason for developing ASP.NET based websites is the controls just to be dragged-dropped and used. This user friendly nature of asp.net gets bottle-necked while Ajaxifying Websites. For this, we use the ajax control toolkit which comes with several server side controls yet ajaxified. For example : cascading dropdown, accordian, etc.
Using other controls through third party tools like telerik is possible but almost all of them (except ajax control toolkit) charges for using the controls  by this way or by that way, thus limiting the use for beginners. Now comes the new open source USER-INTERFACE package :- JUICE UI. 
The first version of JUICE released on 28^th Feb 2012 succeeded with couple of other versions has gained a quite appreciable popularity in the web-development world. The Latest Version as on 26^th Oct is JUICE UI 1.1.1 released on 17^th oct 2012.


Usefulness of JUICE
JUICE is an Open Source package for ASP.NET server-side controls. Developing user-interactive website with drag-drops, Selectig-Sorting, resizing ,etc functionality had never been so easy with ASP.NET. Controls with their functionality can be viewed from here. 
JUICE-UI aims at providing all jQuery UI widgets in the form of ASP.NET server side controls.

Controls


Installing :
JUICE-UI encourages the installing of the package through NuGet which is a visual studio plugin used for getting new/updates of tools/add-ons for visual studio.
You can install JUICE-UI through NuGet : explained here.
Else you can download the files attached below and follow the steps and screenshots.