BOTW Zelda Rig is a free Maya rig based on the Breath Of The Wild version of Zelda. Made by Christoph Schoch.
The Zelda Rig is a free Maya rig made by Christoph Schoch and is available on his Gumroad page
The Link Rig is a free Maya rig made by Christoph Schoch and is available on his Gumroad page
MocapX is a Facial motion capture app for the iPhone that streams the mocap data to Maya in real-time
Grease Pencil Rigs are a free set of basic rigs for Blender 2.8 that are for use with Grease Pencil. They are aimed to ease the drawing of characters by showing construction lines which you can use for reference while drawing.
AnimChallenge is a Facebook group that features a monthly animation challenge as well as a dedication to learning within the animation community.
Johan The Dog is a free quadruped rig for Maya for use in non-commercial projects.
Advanced Skeleton has been used to rig creatures, props, vehicles and just about anything since 1999. It is free to download but if you want to use it for a commercial project you will have to buy a license.