Starting from the Q3 '08 release, the jQuery library is an integral part of RadControls for ASP.NET AJAX. We've posted instructions on how to use the included version in your code and how to enable IntelliSense.
The bad news is that the instructions for enabling IntelliSense no longer work with the Q1 '09 version. The reason is that Visual Studio 2008 has a problem with parsing the jQuery library from version 1.3 and up. This required us to come up with a new way to enable IntelliSense. The good news is that the new approach is much cleaner and doesn't require external files at all.
To include jQuery on your page and enable IntelliSense you need to grab the latest internal build (version 2009.1.331 and up) and add these script references:
<asp:ScriptManager runat="server" ID="ScriptManager1">
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
jQueryInclude.js will replace jQuery (the global $ variable)
with the version embedded in Telerik RadControls!
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
What we did was to add the Visual Studio documentation (jQuery-vsdoc.js) in the assembly. Visual Studio now happily ignores the original script file and uses the -vsdoc version to generate the IntelliSense hints. This means less work for you too, as there's no need to download the help file separately.
UPDATE: You'll need this hotfix for IntelliSense to work: KB958502-JScript Editor support for “-vsdoc.js” IntelliSense documentation files.