Youtube has a tremendous number of gymnastics videos. In fact, many dedicated gymnasts are known to constantly be looking at gymnastics videos of the best US and world men’s gymnasts.
There are many online resources for gymnasts:
DrillsandSkills.com – list of various men’s gymnastics skills and their difficulty rating (A, B, C, D, etc.)
HybridPerspective.com – Dr. David Tilley combines his extensive gymnastics background with his doctorate level of physical therapy to provide helpful tips and insights into injury prevention.