Since manually changing the host every time I want to test an ASP.NET or Silverlight application is so tedious, I wrote this little bookmarklet to do that work for me:

javascript:(function(){window.location=window.location.toString().replace('localhost', 'ipv4.fiddler');})()

Paste that (as a single line) into the URL box of a favorite in IE and you’re one click away from tracing the requests between your browser and your local development web server.

I’ve been doing a lot of Silverlight work recently so have found this especially useful to debug the interactions between the client and the server.