There are a couple of other tools worth pointing out as well
- Fiddler2 a web debugging proxy written by one of the PM’s on the IE team
- IE Developer Tool Bar the Microsoft IE Developer Toolbar. There’s lots of info on it here
- IE6 and IE7 Virtual PC images
- AjaxView a great tool from MS Research for remotely monitoring web2.0 applications for doing perf work
- Nikhil’s Web Development Helper is an add-on that helps AJAX and ASP.NET developers see what is going on with their code
Hope this helps!