Weather Underground - Weather Underground is committed to delivering the most reliable, accurate weather information possible. Our state-of-the-art technology monitors conditions and forecasts for over 60,000 U.S. and international cities, so you'll always find the online weather information that you need.
National Oceanic & Atmospheric Administration (U.S. Department of Commerce) - A government website that provides information on: weather, ocean, satellites, fisheries, climate, et.
NOAA's Raster Navigational Charts - In the United States, all official nautical paper charts produced by NOAA's Office of Coast Survey (OCS) are available in raster format. A fundamental tool of marine navigation, NOAA's Raster Navigational Charts (NOAA RNCs™) are produced by scanning at high resolution the original color separates, which are used to print the paper charts. NOAA adds to the digital raster file such features as data describing the chart, its datum, projection, and its geo-reference. Geo-referencing enables a computer-based navigation system that is connected to a GPS to locate and display on the chart image on screen the vessel's exact position.
http://www.sonar.org/ - International Sonar Class Association
http://www.shumwaymarine.com/sonar/ - Shumway Marine is the exclusive US distributor of Sonar sailboats. Find useful information about Sonar Sailboats
http://www.brucekirbymarine.com/sonar.html - Description and History on Sonar sailboats.