I’ve been working with ASP.NET for a while now, and while I enjoy it, I also try to look outside of the “normal” zone to discover new things. One thing you might be interested to do is to contribute to the community around the framework. This will let you understand the intricacies of the platform and the paradigms behind it.
ASP.NET allows you to build great web site and applications.
To take a look at the source code for MVC, Web API and Web Pages, start here.
Released versions are accessible here.

These products are developed by the Microsoft ASP.NET team, in coordination with open source developers. That team is assigned to the Microsoft Open Tech Hub. MS Open Tech was created on April 12, 2012. Its president, Jean Paoli, is the co-creators of the XML 1.0 standard with the World Wide Web Consortium (W3C). Jean joined Microsoft in 1996 and is also a co-creator of InfoPath.  Read Jean’s note here.

If you use Git, the following command will clone the entire repo and download the source code on your machine:

git clone https://git01.codeplex.com/aspnetwebstack.git

If you want to contribute, go here.
If you plan to contribute with bugs reporting, then learn a bit about good bug reporting here. To see the roadmap of MVC, Web API and Web Paged, check that.

Contributors are identified and you can see them here.