You can get information on copyrights from the United States Copyright Office.
Another place to get information on copyrights is Nolo's Law Center for Trademarks and Copyrights
Thomson & Thomson, one of the premier trademark and copyright services, provides a wide range of information about copyrights in the IP Fundamentals area.
Many law firms that practice intellectual property law have extensive information on their Web sites for the subjects covered in their practice, including information on patents, trademarks, copyrights, and service marks and trade secrets. To find these law firms, you can search for intellectual property attorneys at Lawyers.com or conduct a search on Google and Yahoo! for “intellectual property attorneys.”