The U.S. Patent & Trademark Office (PTO) has a wealth of information available online. General information about patents may be found from this page. One may also search issued patents, or find information about trademarks and registering a trademark. State registration of trademarks may also be available.
A publishing company having a line of books on various aspects of intellectual property law is Nolo Press. This firm has no connection with Nolo Press. While the content of books can be of great assistance, it is not a substitute for professional advice.
The registration of copyrights is the duty of a branch of the Library of Congress.