The Trade Secrets Homepage tries to be "a comprehensive site of trade secret law and information."
The BNA Corporate Practice Series includes a pamphlet called Trade Secrets: Protection and Remedies (No. 43). BNA also publishes Trade Secrets: A State-by-State Survey.
The leading treatise on U.S. trade secret law is Milgrim on Trade Secrets. For other countries, Trade Secrets Throughout the World (West) explains the trade secrets laws of 30 foreign countries, plus the U.S. For more information, search recent law review articles and the Internet.
Most states have adopted some version of the Uniform Trade Secrets Act. The Legal Information Institute posts a chart showing where you can find those laws in each state's statutory code.
The Practical Law Company provides a summary of the trade secret laws for many states (subscription only).