This is one of the football tackling drills I picked up at a clinic in Arizona last fall. Try this out with your team tonight!
Here is a good open field football tacking drill:
Have your quarterbacks in one line and the receivers, tight ends, running backs in another line running some passing tree routes.
Have your defensive backs and linebackers about 25 yards down field; cone off a playing area about 25 yards long and about 40 yards wide.
The QB will call a pass pattern and throw the football to your skilled players and they will attempt to score against 2 defenders in the open field past the cones.
You can keep score with the offense and defense and also put in some line man to block against the defense. This football drill can be modified and should only be done after you have taught proper tackling and blocking techniques.