Free Kids' Books From HarperCollins

http://www.harpercollinschildrens.com/HarperChildrens/Members/firstlook/index.aspx

This link is actually for your kids to sign up -- they'll ask for the child's email address and DOB, then they'll ask for the parents' email address. The parent has to click "I approve" in an email to their address before the child can join.