I say go and buy Tom Emanski's Baseball World's Defensive Drill Video. You know that one that is enthusiastically endorsed by Fred McGriff. I mean if this video can teach kids to throw a ball into a garbage can laying on the ground at home plate all the way from centerfield, then it must be able to teach them how to properly throw.
http://espn.go.com/page2/s/caple/030709.html