These resources are particularly useful for researching the performance and policies of U.S.
Federal Government agencies and programs. (Descriptive quotations below are from the
U.S. Government Manual.)
Some other Federal Government publications "about" the Federal Government can be found here.
The CBO "provides the Congress with assessments of the economic impact of the Federal budget... analyses of alternative fiscal, budgetary, and programmatic policy issues." Topic areas include Social Security, welfare, health, national security, etc. See the "Publications" option (top of page), which includes browsing and searching capabilities.
Congress created the CRS to serve its needs for "nonpartisan and objective research and analysis... by providing timely and confidential research and analysis to Members, committees, and their staff on all public policy issues of interest."
GAO is "the investigative arm of the Congress and is charged with examining all matters relating to the receipt and disbursement of public funds." Reports and testimony are excellent non-partisan sources; use the "search" option in the upper-right corner.
There are inspectors general who conduct audits, investigations, and inspections within about 60 Federal agencies. This page, which is provided by the coordinating IGnet, offers a list of available IG Web sites in various agencies, where you can find reports on that agency. There is no way to search across all the IG agency Web sites, although the "Search IGnet" option (upper right) allows you find materials in the IGnet site itself.