"U.S. Reports" and "U.S. Reports Slip Opinions" are the official publications of Supreme Court decisions. Via HeinOnline you can access the full text of all decisions, from 1754 (Volume 1) to the present.
Oyez is a website with Supreme Court audio recordings of hearings. The site includes hearings since 1980 and the goal is to eventually include hearings since 1955. For selected cases argued before 1979, and for nearly all cases argued after 1979, the site provides unofficial versions of the transcripts, along with the audio whenever available. Once you have found your case, click on the "Expanded View" to obtain the printed transcript of the oral arguments. For "Opinions", look for the section called "Case Basics" in the lower left corner of the case's page, and click on the link provided for "Opinion."
The Legal Information Institute is a not-for-profit based at Cornell Law School. It is known internationally as a leading “law-not-com” provider of public legal information. The website offers all opinions of the United States Supreme Court handed down since 1992, together with over 600 earlier decisions selected for their historic importance.