UPDATE: The steps explained below don't work with CRM 2013.  However, Scott has a blog post which shows you how to get it working again:

http://develop1.net/public/post/Fiddler2-The-tool-that-gives-you-Superpowers-Part-2.aspx

One of my last posts was sharing how I use Visual Studio to debug CRM web resources:

http://blogs.msdn.com/b/devkeydet/archive/2013/06/19/eureka-f5-debugging-of-crm-javascript-web-resources.aspx

This approach was one of those discoveries that makes us developer types get a little excited because it allows us to do something we do repeatedly in a much more efficient fashion.  I just came across another one of those EUREKA moments thanks to Scott Durow (@scottdurow) and some his promising new http://www.sparklexrm.com project. 

BTW, Scott’s the man behind Ribbon Workbench for Dynamics CRM.  It’s the best Ribbon editor out there in my opinion.  I digress…

I was reading through http://www.sparklexrm.com/s/Tutorials/SetUpNewProject.html and discovered a little gift from Scott at the end of the walkthrough.  Steps 9-14 explain how to use www.fiddler2.com to let you debug changes to web resources without ever having to deploy them to Dynamics CRM.  How?  Steps 9-14 explain it.

Combine this with my post on F5 debugging from Visual Studio and you nearly have web resource developer productivity nirvana.  I just tried combining the two approaches.  It works beautifully!  I was able to make changes to JavaScript, hit F5, debug right in Visual Studio, and repeat over and over again.  I did this all without ever having to deploy the JavaScript file to the server.  Because of it, I was able to iterate on my changes in a fraction of the time CRM developer typically spend.  Try it yourself!

@devkeydet