SCOTUSblog's Golan v. Holder page has links to all the relevant documents, including the opinions, a transcript of the oral argument, and all the amicus briefs, including one jointly filed by the ALA, ARL, Internet Archive, University of Michigan, and the Wikimedia Foundation which lays out in stark detail just how important this case is for the future of our understanding of copyright law in general and public domain works in particular. They've also got a very useful summary of the decision.
Coverage from the New York Times, Washington Post, Chronicle of Higher Ed, Associated Press, Techdirt. The latter is a particularly good synopsis, and I agree with their conclusion that the majority opinion simply doesn't seem to take into account how copyright law operates today.
[Update: Another important piece on this, from Kevin Smith at Duke, "Losing Our Focus"]