Aviation Weather Center
Weather guide for American pilots.
http://aviationweather.noaa.gov/

Aviationwx.com
Internet-based real-time weather tracking, ETOPS and colour-coded cloud top imagery.
http://www.aviationwx.com/

Bureau of Meteorology
A comprehensive list of aviation weather services for Aussie aviators.
http://www.bom.gov.au/reguser/by_prod/aviation/

CheapTickets
Check to see if there are any weather delays at the airport before you set off.
http://www.cheaptickets.com/trs/cheaptickets/content/travel_tools/main_travel_tools.xsl

Dispatcher's
Weather links for aircraft dispatchers worldwide.
http://www.dispatcher.org/brief/adfbrief.html

FlightBrief.com
A commercial service offering weather information for aviators.
http://www.flightbrief.com/avcast_new.html

Met Eireann
Weather reports for civil, military and general aviation.
http://www.met.ie/aviation/default.asp

Met Office
Find out what the weather in the sky above Britain is like.
http://www.met-office.gov.uk/aviation/index.html

MetFlight
Subscription service offering weather reports for Kiwi pilots.
http://www.metra.co.nz/metflight/MetFlight.html

Pilot Weather
Check out the weather before you take off in to the sky. Subscription service.
http://www.accuweather.com/avibinf/intro.asp

Skylink
Specialized weather reports, including aviation weather reports.
http://skylinkweather.com/

South African Weather Service
Meteorological information for South African pilots.
http://aviation.weathersa.co.za/

The Weather Channel
Check out the current weather conditions at airports worldwide.
http://www.weather.com/activities/travel/businesstraveler/?

Weather Office
Flight planning and weather reports for Canada courtesy of the Weather Office.
http://www.flightplanning.navcanada.ca/