In addition to administering and regulating, federal agencies often employ researchers who produce analysis using agency data. What follows is, no doubt, an incomplete listing of agency-hosted collections.
Catalog of Government Publications
The finding tool for federal publications - some of the working paper series linked above will be included, others may not be. Combine a topical term with the phrase "working paper".
Research reports prepared for Congress provide excellent background information on the topic covered. Examples of agencies that produce reports include the Congressional Budget Office, the Government Accountability Office, and the Congressional Research Service.
Congressional Research Service (CRS) reports are non-partisan, high-quality research on timely issues. Prior to passage of P.L.115-141 (03/23/2018) these reports are not routinely released beyond Congress and several organizations worked to make access to the documents more widely available. What follows are links to several sources for CRS reports in digital format.