I have the most adorable little 10 month old niece, and I want to be the best auntie possible so I've been reading up on the science behind early childhood development. I've found the Harvard Center on the Developing Child website to be really interesting. I won't pretend to understand everything, but I've enjoyed reading about it:

http://developingchild.harvard.edu/library/multimedia/interactive_features/coreconcepts/