As a concept or to go into a business? Once more, I can't emphasize enough that if you are interested in the CM, read the Compute Module forum. That's where the active CM discussions take place.
Tons of them. Google is your friend. Plus, of course, innumerable books. You could probably find college or "adult education" courses on it as well. If you have a local Coder Dojo or Code Club near by, pretend to be 10 years old and they'd probably teach it to you.