I read ScottGu’s blog entry (http://weblogs.asp.net/scottgu/archive/2008/11/21/jquery-intellisense-in-vs-2008.aspx) a while back, and it seems to imply more functionality than I’m seeing. I have VS2008 and its service pack installed, and I am using a new MVC project with the RC1 version of asp.net MVC. I referenced the jquery-1.2.6.js script, and I can see intellisense when I type ‘$.’ but anything after that shows nothing. This isn’t particularly helpful for a jquery novice like me, so I’m hopeful that I’ve just forgotten something.
For example, when I try to use the specific script example in Scott’s blog post: 
(source: scottgu.com)
I don’t get any intellisense action for the ‘attr’ that he shows the tooltip for. Should I expect this intellisense help, and if so, what can I look for to address the problem?
Here’s my script reference. It’s declared in a master page, FWIW, and my attempted use of jquery is in my page that references this master page.
<head runat='server'> <meta http-equiv='Content-Type' content='text/html; charset=utf-8' /> <link href='~/Content/styles/default.css' rel='stylesheet' type='text/css' /> <script type='text/javascript' src='~/Content/scripts/jquery-1.2.6.js'></script>
Have you installed the jQuery-vsdoc.js file as well (in the same location as jquery-1.2.6.js)? This file contains the comments for intellisense. It’s documented in step 3 of ScottGu’s blog post.
Update:
And you also installed the Visual Studio patch?
For me it works (as shown in ScottGu’s blog), although I’m using a website project, not MVC. I added the script reference in the master page:
I get intellisense in both the master page and in content pages (tried it with the code you put in your question).