RadSplitter
for asp.net ajax
The Telerik Splitter control for ASP.NET AJAX provides a clean and elegant way to
separate content within your Web application. Control the layout of your UIs with
multiple resizable areas and sliding, expand/collapse capabilities, dockable panels
just like in Visual Studio .Net. Each layout can be indefinitely nested with splitters,
whose state is automatically persisted on the server and can be saved/loaded through
the extensive API.