Needs review
Source: Dragon Magazine #343

Description: You can strike at nearby opponents in a blindingly fast spinning assault and follow it up with extra attacks.

Prerequisites: Dodge, DEX 13, Combat Expertise, INT 13, Mobility, Spring Attack, Whirlwind Attack

As part of a whirlwind attack full-attack action, you can make all of your additional attacks based on your base attack bonus in addition to your normal attacks granted by the feat. For example, a 12th-level fighter with Improved Whirlwind Attack can make all his normal Whirlwind Attacks (each at +12 plus Strength and other modifiers) and then make the two additional attacks he gains from having a high base attack bonus (at +7 and +2 plus Strength and other modifiers). He does not get to make these additional attacks against every opponent; he only gets the two attacks at the end of his whirlwind.

Special

A fighter may select Improved Whirlwind Attack as one of his fighter bonus feats.