In the MSDN Belux Flash & Events - Volume 9, Number 22, I found following "nice to have" tools:

The Internet Explorer Developer Toolbar.  A must have for web developers.  This toolbar provides you several features like:

• Exploring the DOM
• Viewing HTML object details
• Validating HTML
• ....

http://www.microsoft.com/downloads/details.aspx?FamilyID=e59c3964-672d-4511-bb3e-2d5e1db91038&displaylang=en

Snippy - Visual Studio Code Snippet Editor.  A code editor for Visual Studio 2005.  Snippy can be used to add new snippets or to modify previous created snippets.

http://www.gotdotnet.com/codegallery/codegallery.aspx?id=b0813ae7-466a-43c2-b2ad-f87e4ee6bc39