In the last few years I’ve become more and more interested in and copyright law, both on the tecnology/patent side and the art/imitation side. Kirby Ferguson’s TED Talk, Embace The Remix, is required viewing if you’re interested.
According to The Center for the Study of the Public Domain nothing entered the public domain in 2013:

What is entering the public domain in the United States? Nothing. Once again, we will have nothing to celebrate this January 1st. Not a single published work is entering the public domain this year. Or next year. In fact, in the United States, no publication will enter the public domain until 2019. Even more shockingly, the Supreme Court ruled in 2012 that Congress can take back works from the public domain. Could Shakespeare, Plato, or Mozart be pulled back into copyright? The Supreme Court gave no reason to think that they could not be.
via Open Culture