The Congressional Research Service is an agency of the Library of Congress which provides analytical, non-partisan reports on topics of interest to members of Congress and their staff. While they do not maintain a public website for dissemination of these reports, there are a number of free and subscription sites where you can find CRS reports. You can also request copies from your Congressional Representative or local library. Selected reports have been made available on the web by various organizations.
See also: GAO (General Accounting Office) Reports
Congressional Research Service Reports, Hosted by UNT Libraries : The University of North Texas Library hosts an award-winning site where many CRS reports are browsable by topic and searchable by full text. This is the best starting point.
CRS Reports from the State Department (Foreign Relations)
CRS Reports on Science - Federation of American Scientists
CRS Reports on Global Security - Selected listing of reports on the environment, foreign relations, the military, space, science and the U.S. Government with links.
Agriculture & Food Issues - National Agricultural Law Center
Archive-It: These "harvested" CRS reports collected by Stanford University will eventually be added to the Internet Archive.
EveryCRSReport.com: EveryCRSReport.com includes 8,484 CRS reports and growing. It includes every CRS report that’s available on Congress’s internal website.
National Library for the Environment (NLE) - Congressional Research Service Reports on the Environment : The NLE has over 1,200 CRS reports on its Web site. These reports relate primarily to environmental topics.