There is a new source for Ninth (9th) Circuit Court of Appeals briefs that can be added to my previous list. Many, many thanks to University of Hastings Law Library and the Law dot Gov team!
This is a work in progress. Don’t forget that PACER is an alternate source for official federal court case filings. Not all law libraries subscribe to PACER, but many do so contact your local public law library for PACER information.