The Congressional Research Service (a division of the Library of Congress) provides high-quality research and analysis for committees and members of Congress. These reports, studies, and issue briefs are succinct and well-researched and many are regularly updated. About CRS
Most of these reports are available on public websites. Some are on commercial online services that are either UW Restricted (HeinOnline) or that require individual IDs and/or passwords (Bloomberg Law).
For more information about finding CRS reports, see the Gallagher guide on Congressional Research Service Reports.