NOAA Resources:

• National Data Buoy Center
• National Hurricane Center
• Storm Prediction Center
• The National Weather Service
  • Marine Forecasts
  • Charting and Navigation
  • Wind Chill Chart
  • nowCOAST: Real-Time Coastal Data Map Portal
• Office of Coast Survey
• Water Level and Tidal Current Predictions
  • Tide Predictions
  • Current Predictions
• Nautical Charts Online

 
Other Resources:

Navigation and Weather:

• BoatU.S.
  • Hurricane Resource Center
  • BoatU.S. Foundation
• CoastalBoating.net -- many resources for cruisers including weather, navbigation and safety
• Jenifer Clark's Gulfstream -- this service is not free, but Jennifer provides realtime ocean charts and Gulf Stream data which is invaluable to cruisers.
• Johns Hopkins University Applied Physics Laboratory / Ocean Remote Sensing Group -- near real-time presentation of sea surface temperature imagery
• Latitude/Longitude Distance Calculation -- determine the distance between two points on the earth given their latitudes and longitudes.
• Maptech.com -- the creators of the Embassy Guides, ChartKits and navigation software. Also provides an online mapserver which includes nautical, terrain and aeronautical charts.
  • NGA List of Lights
  • Sight Reduction Tables for Marine Navigation
  • USCG Light List
• NWS Marine Product Dissemination Information -- Worldwide weather fax frequencies, schedules, forecasts, radiofax, satellites and other products.
• Rutgers University Coastal Ocean Observation Lab -- real-time satellite data (the main area of coverage is NJ but there is satellite data for all of the eastern U.S. and the Great Lakes.
• Surface Distance Between Two Points of Latitude and Longitude AND Great Circle Distances Between Cities -- calculator
• Tideschart.com