Curling Wave Strike

 
Prerequisite(s): Dex 13+, Improved Trip
 
Benefit: If you trip an opponent in melee combat, you can immediately make another trip attack against a foe within reach at the same total attack bonus as the first trip attempt. This replaces the free attack you would normally get against the tripped opponent. If you successfully trip the second opponent, you do not get the free attack on him either. This feat can be used once per round.
 
Source: Stormwrack