www.chesskid.com is chess.com's partner site for kids, where you can safely monitor your child's privacy etc. as a parent.
The curriculum prepared for children by IMs Pruess and Rench is also an excellent source, and not only for children :)
http://www.chess.com/download/view/chesskidcom-curriculum
My daughter recently asked me to teach her how to play chess. She is 4 and I really don't know if that is too young to learn chess. Does anyone know of any good books, websites, etc. for younger chess students?