CRS report on the topic updated 02/03/2006
See also ALA on this issue.
The Justice Department addresses some of the concerns regarding Patriot Act & libraries at http://www.lifeandliberty.gov/subs/u_myths.htm
The CRS report USA Patriot Act Additional Reauthorizing Amendments Act of 2006 (02/21/2006) also contains information about the Act that pertains to libraries.