plyometrics, boxing footwork, shuffle and stick drills, directional step/stick, and from tcma, dragon stepping which is a form of stomping and isn't really footwork so much as it is intended to build bone density.

the plyo and boxing stuff is the most beneficial.

in tcma, most of the footwork was tied into the forms. over time Ive extracted some of it, but not everything.

boxing is simple and effective and so it is in my opinion the work i prefer.