Recently, MS made a public release of the Ajax view tool and I thought it's surely worth mentioning and spreading the word around.
Overview snippet of the tool …
The goal of the Ajax View project is to improve developer's visibility into and control over their web applications' behaviors on end-user's desktops.
You can find the download and usage information at http://research.microsoft.com/projects/ajaxview/
John’s blog item about Ajax View on the IE team blog has more information regarding the same: http://blogs.msdn.com/ie/archive/2007/08/23/Analyzing-Web-2.0-Applications-with-Ajax-View.aspx