This is a very good introduction to how you can hide yourself - and how much you can hide yourself - from the creepy NSA hooveramatic. Highly recommended.
The point, of course, is not to participate in the unsavory aspects of the 'Net (like The Silk Road). Instead, it's how a group like the Tea Party can communicate with a reduced risk of retaliation from the Fed.Gov. It's a bit annoying that the First Amendment means so little these days that legitimate political groups need to use some of the same tools as Internet scumbags.