There are a lot of ASP.NET MVC Best Practices running around the Internet via blog posts and articles.
A fairly new best practice IMHO for ASP.NET MVC and even ASP.NET Webforms is to use the Microsoft CDN to host the various Javascript Files used in your ASP.NET MVC and Webforms Applications. No reason to burden your own web server when Microsoft and other 3rd parties are willing to help the performance of your web server as well as reduce the bandwidth consumed by hosting Javascript Files for you.
You have the following Javascript / AJAX Scripts on the Microsoft CDN:
- Microsoft AJAX
- jQuery
- jQuery Validate
- ASP.NET MVC 1.0 AJAX Scripts
Here are the current URL's for the ASP.NET MVC 1.0 AJAX Scripts:

Check out details on the Microsoft CDN for yourself here.
David Hayden
Related Info: