GMH2 is an advanced version of the GMH script, specialized in hair modeling & stylizing, created by Phung Dinh Dzung.
animSelector - Free Maya Script
Luca Fiorentini has created animSelector a free Maya script that sets up selection groups and hotkeys for rigs.
Make StretchMesh for Maya Open Source
Help Kickstand to release the open source code for their Maya plug-in, StretchMesh.
IKinema Action for MotionBuilder
IKinema Action for MotionBuilder provides superior retargeting, marker solving and rigging capabilities.