Slate's Dahlia Lithwick has a sharp, balanced column on The PATRIOT Act that's well worth reading in its entirety. Snippets:

While some portions of the Patriot Act are truly radical, others are benign. Parts of the act formalize and regulate government conduct that was unregulated?and potentially even more terrifying?before. Other parts clearly expand government powers and allow it to spy on ordinary citizens in new ways. But what is most frightening about the act is exacerbated by the lack of government candor in describing its implementation. FOIA requests have been half-answered, queries from the judiciary committee are blown off or classified. In the absence of any knowledge about how the act has been used, one isn't wrong to fear it in the abstract?to worry about its potential, since that is all we can know.

When asked by the House Committee on the Judiciary to detail whether and how many times Section 215 has been used "to obtain records from a public library, bookstore, or newspaper," the DOJ said it would send classified answers to the House Permanent Select Committee on Intelligence. The judiciary committee had what it called "reasonable limited access" to those responses, and it reported in October 2002 that its review had "not given any rise to concern that the authority is being misused or abused."

Wanting to learn more, the ACLU and some other civil rights groups filed a FOIA request, arguing that the DOJ was classifying its answers unnecessarily. But this May, a federal judge in U.S. district court in Washington ruled that the DOJ had the right to keep the specifics hush-hush under FOIA's national security exemption. The next day, at a judiciary committee hearing, Assistant Attorney General Viet Dinh did throw a bone to librarians, noting that in "an informal survey of the field offices," Justice learned "that libraries have been contacted approximately 50 times, based on articulable suspicion or voluntary calls from librarians regarding suspicious activity." He did not give specifics on searches of any other establishments.

[Section] 215 does extend FBI power to conduct essentially warrantless records searches, especially on people who are not themselves terror suspects, with little or no judicial oversight. The government sees this as an incremental change in the law, but the lack of meaningful judicial oversight and expanded scope of possible suspects is pretty dramatic.

The whole thing, apparently the first of a series on the act, is here.