(Pls read again. New Link added) "Conspiracy Theories and Falsehoods."The NYT and Conspiracy Theory.

[Democracyinkind]

2. A good starting point

http://books.google.ch/books/about/Conspiracy_theories.html?id=SoyalAxDItYC&redir_esc=y

blurb:

Conspiracy theories have a bad reputation. In the past, most philosophers have ignored the topic, vaguely supposing that conspiracy theories are obviously irrational and that they can be easily dismissed. The current philosophical interest in the subject results from a realisation that this is not so. Some philosophers have taken up the challenge of identifying and explaining the flaws of conspiracy theories. Other philosophers have argued that conspiracy theories do not deserve their bad reputation, and that conspiracy theorists do not deserve their reputation for irrationality. This book represents both sides of this important debate. Aimed at a broad philosophical community, including epistemologists, political philosophers, and philosophers of history. It represents a significant contribution to the growing interdisciplinary debate about conspiracy theories.

In it, you'll find a very apt discussion of prominent methods and concepts used in order to discuss conspiracy theories so far. There's a very interesting discussion of Popper's view in it, too. Certainly not the last word on the topic, but a good place to start.