NOAA. Great source of weather information. Includes past weather map images of major storms.
Excellent site by Johns Hopkins University. High resolution, near-realtime, color NOAA polar orbiting infrared satellite images covering the entire East Coast and Gulf of Mexico.
The official site of the National Maritime Museum in Greenwich, England. Interesting information about navigation. Great resource for historical information about navigation and life at sea.
Execution Rocks weather buoy information, tides, dew point, temperature, wind speed, radar and much more available.