Kiel Figgins Rigs – An amazing selection of free and paid rigs (mostly paid) are available on Kiel Figgins’ website.
Kiel Figgins Rigs (FREE+)
Truong Rigs (FREE+)
Truong Rigs – A massive selection of free and paid rigs all made by Truong
BodyMech Rigs ($40)
BodyMech Rigs are a series of Maya rigs, designed to be perfect for honing in on those body mechanics and body acting skills.
Animator's Resource Kit 