Psychology

• About.com has a startlingly comprehensive, clear, and easily navigable information for psychology, including theories and research methods.
• Flat World Knowledge, one of our favorite resources, also has excellent online textbooks for Introduction to Psychology, Social Psychology, and Research Methods.

Sociology

• Sociology? There’s a Flat World Knowledge for that too. Check out introductory text (in either its “brief” or “comprehensive” form) and one on Qualitative and Quantitative Methods in the field.
• A website stupidly titled edu.LearnSoc.org has ton of surprisingly un-stupid study aids for sociology, most notably a comprehensive list of summaries of Sociological Theories.

Anthropology

• Palomar College has a selection of open tutorials for both Cultural Anthropology and Biological Anthropology that include all kinds of study aids, such as flashcards and quizzes.
• BBC has a fantastic section that serves as an introduction to Archaeology.