Covid-19: For updates and resources, head to UT's Protect Texas Together site.
NB: Failing these sources, to get copies of cert petitions in cases where cert was denied, patrons may need to contact the Supreme Court Clerk's Office at (202) 479-3011 and have the docket number. It is likely that the patron will need to have someone physically go there and copy the document.
Two main sources:
SCOTUSblog: Merit, amicus, and petition granted briefs from 2007 to date; PDF
US Supreme Court > Docket Search: most filings submitted, including merit, amicus, and petition granted briefs, from Nov. 13, 2017 to date; PDF
Lexis+: Briefs, Pleadings, and Motions > Federal > U.S. Supreme Court Briefs
Landmark Briefs and Arguments of the Supreme Court of the United States: Constitutional Law: Online via HathiTrust and KF 101.9 L35
Office of the Solicitor General: All briefs from the OSG 1998 to date (PDF); selected older briefs 1982 to 1997 (html)
ProQuest Supreme Court Insight: Records and briefs from 1975. For the current term, the database will be adding material on an ongoing basis while a case is pending before the Court.
Appellate case files of the Supreme Court of the United States, 1792-1831:
Westlaw: Briefs > U.S. Supreme Court:
U.S. Supreme Court Records and Briefs (1960 to date):
U.S. Supreme Court Records and Briefs (1832 to date): Microfiche holdings
The joint appendix or appendices includes the relevant docket entries; any relevant pleadings, jury instructions, findings, conclusions, or opinions; the judgment, order, or decision under review; and any other parts of the record that the parties wish to bring to the Court's attention.
Lexis: joint appendices beginning in January 1979, with selected coverage from 1936.
Westlaw (SCT-JA): Selected joint appendices from 1982 to present.