George Siemens points to this paper posted just last week from the forthcoming Handbook of Social Network Analysis. Put this book into your wish list if it is as good as this introduction. Marin and Wellman crisply chop through the major elements of social network analysis, conveniently identifying major schools of thought and major approaches along the way. The references won't lead you astray; they are authoritative. Of this excellent paper I have only one quibble: they write "social network analysts argue that causation is not located in the individual, but in the social structure." I would be much more careful with my wording, because causes are located in the individual. What is a mistake, I would argue, is to assign sole causation to such factors. The authors explain, "large number of people acting similarly because they are similar, but as a large number of people acting on one another to shape one another's actions in ways that create particular outcomes." But this is a tiny matter of wording.