University of Virginia
The University of Virginia: The Crowd: A Study of the Popular Mind
A classic psychological text by Gustave Le Bon on crowd behavior, first published in 1896. The full text of this work is organized by chapter.
Other
Massey University: Beyond the Individual Social Antimony
This is a paper discussing Piaget and Vygotsky. It compares their similarities and differences. There is a large section on social origins of development.