National Trade Data Bank
While probably not of much interest to academic economists, this site pulls together a very wide range of information (more than a gigabyte) from more than 25 U.S. government agencies that will be of interest to firms wishing to export from the U.S. Much of the information is fee-based. Obviously, it contains a substantial amount of material that may be of interest to those interested in non-U.S. countries. One can even search the entire database with "natural language requests" (that is, you can query the database as you might a person).
http://www.stat-usa.gov/tradtest.nsf