Since discovering the XML commenting features built into .NET years ago I have been using it to help make my code more readable and simpler for other developers to understand exactly what the code is doing.
Entering /// preceding a line of code causes Visual Studio to insert "summary" tags. It also results in additional tags being generated if you are commenting a method with parameters and a return type.
I already knew that Intellisense would pick up these comments and display them when coding and selecting properties, methods, etc. from a class. I also knew that you could set Visual Studio to generate an XML file containing said comments. Only recently did I begin to wonder if I could generate some kind of readable help files based on these comments I so diligently added.
After searching the web I came across NDoc, an open source project which creates documentation for you based on the XML files generated by Visual Studio. Unfortunately, NDoc has become stale and no longer supported (last release was back in 2005).
Fortunately there is a little known tool from Microsoft themselves called "Sandcastle Help File Builder". This nifty little tool gives you a graphical interface that allows you to specify multiple DLL and XML files from which to generate a MSDN like HTML Help File for your own projects!
You can check it out here: http://shfb.codeplex.com/
If you are curious how to set Visual Studio to generate the above reference XML documentation files simply go to your projects property page and edit as shown below (my paths are specific, you can leave yours at the default values):