Intellicast
Weather conditions on major US highways.
http://www.intellicast.com/DRIVEcast/World/UnitedStates/AllWeather/

Public Safety & Emergency Preparedness Canada
Winter driving tips, including how to keep control of your vehicle, braking and what to pack in a car survival kit.
http://www.ocipep.gc.ca/info_pro/self_help_ad/general/winterdriv_e.asp

Road Weather.com
Current road weather conditions for the United States.
http://www.roadweather.com/

The Weather Channel
Regional motorway weather forecasts.
http://uk.w3.weather.com/activities/travel/driving/

Wetroads.co.uk
An index of splash-down river and low water crossings throughout the UK.
http://vamp.idlers.org/~jaffa/
http://www.wetroads.co.uk/