Here are some helpful links for further reading:
The U.S. Copyright Office examines and registers hundreds of thousands of copyright claims in books, music, movies, software, photographs, and other works of authorship each year. In fiscal year 2011, the Office processed more than 700,000 registration claims. The Office administers several statutory licenses that manage and disperse private monies, including those pertaining to copyright owners’ rights in programming on broadcast television signals that are retransmitted by cable operators and satellite carriers. It also provides basic copyright information services to the public in a variety of ways.
The United States Patent and Trademark Office (USPTO) is the federal agency for granting U.S. patents and registering trademarks. In doing this, the USPTO fulfills the mandate of Article I, Section 8, Clause 8, of the Constitution that the legislative branch “promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.” The USPTO registers trademarks based on the commerce clause of the Constitution (Article I, Section 8, Clause 3).
Creative Commons is a nonprofit organization that enables the sharing and use of creativity and knowledge through free legal tools. Its free, easy-to-use copyright licenses provide a simple, standardized way to give the public permission to share and use your creative work — on conditions of your choice. CC licenses let you easily change your copyright terms from the default of “all rights reserved” to “some rights reserved.”