Animation Comparisons is a YouTube playlist that includes videos showing how various animations look in multiple different games. Great for reference.
Animation Comparisons
VGAR
Video Game Animation References is a YouTube channel focused on sharing various types of animation reference from video games (Idles, attacks, movement.. etc)
50 Ways To..
50 Ways To.. is a series of videos by Kevin Parry showing how much variation there is in the simplest thing. A fun and extremely useful resource for animators looking for inspiration
Challenger Jacobus
Challenger Jacobus is a Youtube playlist made by Eric Jacobus where he performs movesets from beat-em-up games in real life. Great resource for animation reference!
GreenScreen Animals
GreenScreen Animals is an extensive library of domestic and exotic animals video footage in high definition.
Sakugabooru
Sakugabooru is a huge animation archive used by fans and animators alike to upload and view animation clips from anime movies and shows.
Endless Reference
Endless Reference is a Youtube channel that focuses on animation reference. Lots of great human locomotion videos from different angles
Bodies in Motion
Bodies in Motion is an ongoing photographic project that aims to document the power, beauty and possibility of the human body in motion. It is freely accessible to all visitors at preview resolution or you can subscribe for higher quality images.
Animator's Resource Kit 