Animators Survival Kit - Richard Williams
When I first discovered this book, it was like hitting the jackpot and finding treasure everywhere! Best standalone book on animation that covers all the core principles.

The Illusion of Life: Disney Animation - Frank Thomas and Ollie Johnston
Great insight to the wonders of Disney Animation.

The Artists's Complete Guide to Facial Expression - Gary Faigin
This book completely changes the way I perceive facial expressions. Incredibly detailed and full of great references. Highly recommended!

Film Directing Shot by Shot: Visualizing from Concept to Screen - Steve Katz
Learning how to stage your shots and storyboarding are a great way to improve your animation! This book is more film oriented, but it sure helps to learn from that perspective.

Drawn to Life - Walt Stanchfield
Some really good advice on 2D drawings, gestures and (some) animation.

Flashdeck
My other website which hosts some of my previous animations. It is most well known for the Counter-Strike parodies I animated when I was younger.
http://flash-deck.com