Improved Shield Bash( Defenders of the Faith: A Guidebook to Clerics and Paladins, p. 20)
You can push opponents back by bashing them with your shield.
Power Attack (PH) ,
Divine Shield (DF) ,
Any shield bash you make with a small or large shield also affects your opponent as if you had performed a bull rush. You don't actually move into your opponent's square or incur attacks of opportunity for the bash. You also can't move your opponent back more than 5 feet, nor can you move along with the defender. You can't use this feat with a buckler.