There are some big rules changes being rolled out this fall. The two biggest are a prohibition against blind-side blocks with any part of the body except for open hands. No more leading with the shoulder or forearm on a crack-back block, even if that block lands squarely in your opponents stomach.
I predict that this rule will be fairly tough to enforce, and only screamingly obvious calls will be made. Nonetheless, it is another major rules change in the name of safety.
Also, driving the ball into the ground on an on-side kick to create a pop-up is no longer allowed.
Here's a video with an excellent explanation of the rules change. There's a guy in Hawai'i who releases these for high school football officials. The video is great, buy my main observation is that the quality of film in Hawaiian high school football is excellent.