Glimpse is the open source diagnostics platform of the web. You can use Glimpse to see what is happening inside a web application on both the server and client side. It's like Firebug but with configuration, routing, and profiling information from the server included. Nik and Anthony run the project, and they recently pushed out Glimpse v1.0.1.
The current version of Glimpse works well with ASP.NET MVC 4.
The first step is to install the Glimpse.MVC3 package using NuGet (yes, MVC3 will work with MVC4).
The second step is to use your web browser to visit /Glimpse.axd in your application and click the "Turn Glimpse On" button.
The last step is to visit any page in your application and click on the little Glimpse icon that will appear in the bottom right of the page. Clicking the icon opens up the Glimpse dashboard with server configuration, routing, profiling information, and other diagnostics showing in a tabbed interface.
The direction and extensibility of the Glimpse project make Glimpse particularly exciting. There are very few restrictions on what Glimpse can't diagnose, so if there is a feature you'd like to see feel to jump in on the Glimpse GitHub project. I hope to cover some of the server-side extensibility points in a future post.