Government

The Alaska Division of Fish & Wildlife Protection
The Argentine Maritime Authority
The Auckland Police Maritime Unit
The Australian Shipping Registration Index
British Waterways Home Page (Agency in charge of Britain's canals)
The California Department of Boating and Waterways
The Canadian Department of Fisheries and Oceans
The Canadian Hydrographic Service
The Clark County Sheriff's Office Marine Patrol (Washington)
El Govern Balear
Falkland Islands Government
The Finnish Maritime Administration
The Florida Fish and Wildlife Conservation Commission
Georgia Fishing and Boating Permits Online
The Hong Kong Marine Department
The Hong Kong Shipping Register Index
Intergovernmental Oceanographic Commission (Of UNESCO)
International Council for the Exploration of the Sea
International Maritime Organization (International)
Marine Accident Investigation Branch (UK)
The National Vessel Documentation Information Center
The NOAA's National Marine Sanctuary Program
OceansCanada (Comprehensive guide to everything oceans)
The Ohio Department of Natural Resources Division of Watercraft
The Oregon Department of Fish and Wildlife
The Oregon State Marine Board
The Pennsylvania Fish & Boat Commission (PFBC)
Service Hydrographique et Océanographique de la Marine
The Transportation Safety Board of Canada (Incident reports, more)
The UK Department for Transport, Local Government and the Regions
The United States Army Corps of Engineers Information Network
The US Army Corps of Engineers Inland River Home Page
The US Army Corps of Engineers Portland, Oregon District
The US Army Office of the Chief of Transportation
US Maritime Administration
The US Transportation Command
US Vessel Documentation Information by ID Number
US Vessel Documentation Information by Name