The Congressional Research Service is a legislative branch agency within the Library of Congress. The CRS performs public policy for members of Congress on a nonpartisan basis. (N.B. Two other major congressional support agencies are the Congressional Budget Office and the Government Accountability Office.)
CRS reports include Issue Briefs, Research Memos, and Reports (Short and Long). Their purpose is to clearly define an issue in the legislative context. CRS reports are not released as a matter of course; generally there is no official public access to them.
Here are some places to find CRS reports online:
ProQuest Congressional. (1916-present) Includes citations for CRS reports contained in other congressional publications or reprinted as congressional committee prints.
University of North Texas Digital Library. (1990-present) Aims to provide integrated, searchable access to many of the full-text CRS reports that have been available at a variety of different websites since 1990.