Sam & Amy Rigs are another great set of rigs made by Gabriel Salas
Sam & Amy Rigs
Henry Rig (Free)
Henry rig is a free rig made by students from Cogswell University
Dana & David Rigs
Dana & David are rigs made by Gabriel Salas to help balance the limited choice in terms of race that animators have when picking a character rig.
AnimProps
AnimProps is a website where 2D and 3D artists can create an account for free to share, sell or purchase artwork. A big resource for animation rigs.
Kit Rig (Free)
Kit Rig is a free rig for Maya. Available from the website animprops.com
Built By Colossus Rigs
Built By Colossus Rigs are free and paid Maya rigs available for download. Founded and run by Roman Jeffery.
BOTW Link Rig
BOTW Link Rig is a free Maya rig based on the Breath Of The Wild version of Link (similar to the previously posted Zelda Rig). Made by Christoph Schoch.
Agora Studio Rigs
Agora Studio have been creating a bunch of Maya rigs and releasing them for free primarily to be used in the AnimChallenge. Check them out HERE
BOTW Zelda Rig
BOTW Zelda Rig is a free Maya rig based on the Breath Of The Wild version of Zelda. Made by Christoph Schoch.
Animator's Resource Kit 