I've just finished writing a web server in C#. Its pretty basic and only serves static content like html, xml, and images at the moment. I would like to implement a dynamic language, however. I'm trying to choose between one of the following:

ASP.NET
PHP
Python

I'd prefer to implement PHP or Python because I am much more familiar with those, however I would like to implement whichever might be easiest. How would I go about adding this functionality to my server, and which of the three languages would be the easiest to implement?
EDIT: this is not about what language i want to do web programing in, this is about what language i want to let people who use the server program in. I would like to be able for the server to serve applications written in either asp.net, PHP or Python.
Have you considered boo? It has a very configurable compiler and there are some good OSS examples out there (for example the brail view engine for Monorail & ASP.NET MVC).
C# Web Server: Implementing a Dynamic Language