another great book is updated yearly [i think] by AIGA and is called "Graphic Artists Guild Handbook: Pricing & Ethical Guidelines"... the most recent is the 12th edition
the last few editions have started to include "digital media" and other sections that relate to motion design... there is a "look inside" feature on Amazon that shows the index of topics covered. Very useful for writing contracts, etc. and even has some pricing guidelines... always a good idea to have things in writing - keeps everyone's expectations in check and makes sure that you get paid for the amazing work you do!
AIGA site: http://www.gag.org/pegs/index.php
hope that helps!