The Official 2016 Playing Rules of the National Football League book has been made public, for your holiday reading enjoyment. If you just want to hone your knowledge of the new rules for the coming season, page 2 has that summary. They are listed here:
1. It is now a delay of game penalty if a team is erroneously granted a timeout.
2. The offensive and defensive play callers can use the coach-to-helmet communications system regardless of whether the coach is in the booth or on the sideline.
3. There is no longer a five-yard penalty for illegally touching a pass after being out of bounds and then re-establishing inbounds, but it is a loss of down.
4. The line of scrimmage for extra point kicks is permanently the 15-yard line.
5. Touchbacks on kickoffs are now moved to the 25-yard line.
6. All chop blocks are illegal.
7. The horse-collar tackle rule now includes a defender grabbing the jersey at the name plate or above.
8. A player who gets two fouls for certain kinds of unsportsmanlike conduct is automatically ejected.
9. Multiple spots of enforcement for a double foul after a change of possession have been eliminated.
The full 2016 rule book is available as a PDF here.