Chicago’s American Machine Tools Corporation buys, sells, ships, and repairs heavy machine tools all over the world. They also maintain a curriculum of free, online, non-brand-specific operator education materials, including the best general How to Use a Milling Machine page I’ve seen. There are no videos, but personally I prefer old-fashioned text and diagrams for this purpose. If you are interested in movies, however, MIT’s Introduction to the Mill has some good stuff.