The material below is Open Game Content from a 3PP Source
You can strike two adjacent foes with a single swing.
Prerequisites: Str 13, Power Attack, base attack bonus +1.
Benefit: As a standard action, you can make a single attack at your full base attack bonus against a foe within reach. If you hit, you deal damage normally and can make an additional attack (using your full base attack bonus) against a foe that is adjacent to the first and also within reach. You can only make one additional attack per round with this feat. When you use this feat, you take a –2 penalty to your Armor Class until your next turn.
The material below is Open Game Content from the System Reference Document.
Prerequisites: Str 13, Power Attack.
Benefit: If you deal a creature enough damage to make it drop (typically by dropping it to below 0 hit points or killing it), you get an immediate, extra melee attack against another creature within reach. You cannot take a 5-foot step before making this extra attack. The extra attack is with the same weapon and at the same bonus as the attack that dropped the previous creature. You can use this ability once per round.
Special: A fighter may select Cleave as one of his fighter bonus feats.