Free full text books by Piaget available on the internet

The Origins of Intelligence in Children (1952)

http://www.archive.org/details/originsofintelli017921mbp

The Psychology of Intelligence (1960)

http://www.archive.org/details/psychologyofinte002598mbp

The Moral Judgment of the Child (1932)

http://www.archive.org/details/moraljudgmentoft005613mbp

The Child’s Conception of Physical Causality (1930)

http://www.archive.org/details/childsconception007953mbp

The Language and Thought of the Child (1926)

http://www.archive.org/details/languageandthoug007529mbp

The Growth of Logical Thinking From Childhood to Adolescence (1958)

http://www.archive.org/details/growthoflogicalt007957mbp