National bouy is always interesting. Impressive to watch the Pacific NW during the winter. 30-50' seas not unusual.
Like wunderground for the NEXRAD coverage.
A few more sites:
From Maine. Great weather info all the time, not just winter:
www.crownweather.com/winter.html
For a good look @ the caribbean:
www.caribwx.com/marine.html
The Storm Prediction Center, Norman, OK:
www.spc.noaa.gov
For worldwide satelite views:
www.weatherimages.org/index.html#avaition.
Boat US also has TS and hurricane tracking, among other things.
I do have to say that the forecaster @ caribwx is a bit full of himself, good info at least.
RF 1