Recently launched, an official website which provides free access to non-confidential briefing papers and reports supplied to members of the US Congress. They are working to add back files.
See the FAQS for details of inclusions and material that will be added.
These are excellent for gaining an understanding of the US legislative process, they include updates and background information on bills and budgets.
They are the equivalent of the really useful research briefings from the House of Commons and Lords libraries (UoL students can get access via https://www2.le.ac.uk/library/find/governmentinformation (look for library Research Briefings)) which are excellent at summarising recent legislation, election results and current topics being debated in parliament. Many have links to background papers and parliamentary reports.