ASP.NET MVC meta tags

I am working with ASP.NET MVC and need a way to programmatically set a page's meta tags (title, description, keywords). I can pass ViewData, but it should handle cases where I don't need keywords or description (which is the real tricky part).

I also would like a way to programmatically include Javascript and css references. Again, there are cases where no Javascript or css files are included.