Kit Badger got a tutorial to help you make your own reactive targets... "When it comes to reinforcing good habits while shooting, Reactive Targets is one of the best ways to do it.  In this How To video, I will go over how to make them...

Reactive Targets can be made pretty easily and on the cheap, and their benefits are many.  They allow the shooter to target discriminate, reinforce good shot placement, shooting till you get the desired effect, tracking targets to the ground and ammo management.  

While they work best in a shoot house or structure, they can be adapted to the flat range as well."