I would like to create a new kind of project type for Visual Studio 2010. I’m not sure if I should be working with the Shell SDK or something else. For example, I want to be able to create a project that I can add files to and have new behavior for build and different behavior when files are clicked and different properties when the project properties dialog is shown. I want to be able to add this project type in a solution that has other C# projects.
Edit: Again, I’m wanting to create a new project type, not a new project template.
You can do some of this from Visual Studio without any SDK at all by creating project templates.
However, this only works for existing project types. New project types can be created using packages and the Managed Package Framework (MPF).
Add-Ins can be used to create further IDE extensions to integrate your package types into the IDE using context menus in Solution Explorer, etc.
If there is a need for any SDK, it would likely be the Visual Studio 2010 SDK that you mentioned: