This video from Old Dominion University shows you how you can share individual elements of your course (Modules, Pages, Assignments, Discussions, Quizzes, etc.) with individual users without adding them to your specific course.
This video from Old Dominion University shows you how to copy content (Modules, Pages, Assignments, Discussions, Quizzes, etc.) from one of your courses (Sandbox course) into another course you can access (Live course).