Extract Deltas

the site says it best, "extractDeltas is a plug-in for Maya which helps with the creation of corrective blend shapes to improve the overall deformation in conjunction with regular skinning. It allows to model the corrective shape based on the deformed pose of a character and then generates a mesh which can be used as a blend shape target before the skin cluster calculation is performed." you can get this here: http://www.braverabbit.de/extractdeltas/