Excellent background resource on the NSA

for those of you wondering about the history of this agency, what it can do, and why its use in domestic intelligence ("spying on US citizens") is really a very scary thing:

The Puzzle Palace : Inside America's Most Secret Intelligence Organization (Paperback)
by James Bamford at Amazon.com http://www.amazon.com/gp/product/0140067485/qid=1134764836/sr=8-2/ref=pd_bbs_2/102-2406502-2244947?n=507846&s=books&v=glance

Quotes from the review (my emphasis):

Amazon.com
In 1947, the governments of the United States, the United Kingdom, Canada, Australia, and New Zealand signed a secret treaty in which they agreed to cooperate in matters of signals intelligence. In effect, the governments agreed to pool their geographic and technological assets in order to listen in on the electronic communications of China, the Soviet Union, and other Cold War bad guys--all in the interest of truth, justice, and the American Way, naturally. The thing is, the system apparently catches everything. Government security services, led by the U.S. National Security Agency, screen a large part (and perhaps all) of the voice and data traffic that flows over the global communications network. Fifty years later, the European Union is investigating possible violations of its citizens' privacy rights by the NSA, and the Electronic Privacy Information Center, a public advocacy group, has filed suit against the NSA, alleging that the organization has illegally spied on U.S. citizens.
Being a super-secret spy agency and all, it's tough to get a handle on what's really going on at the NSA. However, James Bamford has done great work in documenting the agency's origins and Cold War exploits in The Puzzle Palace. Beginning with the earliest days of cryptography (code-making and code-breaking are large parts of the NSA's mission), Bamford explains how the agency's predecessors helped win World War II by breaking the German Enigma machine and defeating the Japanese Purple cipher. He also documents signals intelligence technology, ranging from the usual collection of spy satellites to a great big antenna in the West Virginia woods that listened to radio signals as they bounced back from the surface of the moon.

Bamford backs his serious historical and technical material (this is a carefully researched work of nonfiction) with warnings about how easily the NSA's technology could work against the democracies of the world. Bamford quotes U.S. Senator Frank Church: "If this government ever became a tyranny ... the technological capacity that the intelligence community has given the government could enable it to impose total tyranny, and there would be no way to fight back, because the most careful effort to combine together in resistance to the government ... is within the reach of the government to know." This is scary stuff. --David Wall

The NSA actually sued Bamford to try and make this book disappear. It is more thorough than anything the NSA had. Anything by Bamford is a must read on National Security!