Border Crossing/Entry Data (BTS)
Persons, vehicles and containers entering the US from Canada and Mexico (monthly)
National Household Travel Survey (FHWA)
2009 Survey of daily travel behavior, including trip purpose, mode, trip length, household data, etc.
Statistics on Travel to/from the US (Office of Travel and Tourism Industries - DOC)
US citizens traveling abroad and foreign citizens traveling to the US; included tourism/spending data
National Census of Ferry Operators (BTS)
Includes information on routes, terminals and facilities, vessels, etc. 2010 data is available in a new interface.
Intermodal Passenger Connectivity Database (BTS)
Data on the availability of connections among the various scheduled public transportation modes at each passenger terminal