http://www.simplypsychology.pwp.blueyonder.co.uk/cognitive-dissonance.html
This site provides some information on Festinger's cognitive dissonance theory, with some real world examples. There are some downloadable pdfs on the site. A word of caution however… these are A’ level materials and so are basic and low level (though very clear because of this).
http://psychclassics.yorku.ca/Festinger/
A classic original article from Festinger & Carlsmith. It is always worth reading original papers. If you find it difficult, use it in conjunction with the A’ level site above.
http://psychclassics.yorku.ca/Sherif/
An original article on the Robber’s Cave from Sherif et al. It is always worth reading original papers. If you find it difficult use it in conjunction with the information from the more basic site above.
http://www.stanleymilgram.com/
This site provides the reader with vast amounts of information of the life and contributions of Stanley Milgram, including some controversial materials.