Northwest Airlines Meteorology 
Providing weather forecasting products for the aviation industry, including specialized turbulence and thunderstorm forecasts.
http://www.nwa.com/weatherBase Ops
Aviation Weather for Flight Preparation with TAF Metar Sigmet Radar and Sat-pictures.
http://www.baseops.de/
Data Transformation Corp DUAT
FAA's Direct User Access Terminal service provides free aviation weather and flight planning for certified pilots in the US.
http://www.duat.com
Ace's Pilot Shop Weather Data
Aviation weather and flight planning, including forecasts, observations, weather maps, DUATS briefings, icing, and turbulence.
http://www.acespilotshop.com/wx2.htm
Winds and Temperatures Aloft
By selecting one of over 160 continental cities in the U.S.A. or one of 30 cities in Alaska, you can obtain wind direction, speed, and temperature forecasts.
http://www.usairnet.com/cgi-bin/Winds/Aloft.cgi
Aviation Digital Data Service (ADDS)
An aviation weather graphics site including icing, turbulence, and convection. Also includes a "Flight Path Tool" for pilots.
http://adds.aviationweather.noaa.gov/
Aviation Weather Center
The National Weather Service's aviation weather site with official forecast products as well as experimental products.
http://aviationweather.noaa.gov/
Enflight
Obtain plain-language weather briefings using exclusive WXpert translation. View up-to-date weather graphics. Helps prepare and file flight plans. Available both on the Web and on mobile PDAs (Palm i705, etc.)
http://www.enflight.com/
Pilot's Guide to Aviation Weather Services
An online brochure to help pilots use the "National Aviation Weather System."
http://www.nws.noaa.gov/om/brochures/pilot.htm
SA Weather Service - Aviation
Provides weather services for the aviation industry in Southern Africa. Includes metars, sigmet charts and forecasts.
http://aviation.weathersa.co.za
WSI
Provides pre-flight and in-flight weather information. Aviation weather also available online through WSI Pilotbrief.
http://www.wsi.com/solutions/aviation/
Flying in Europe
Weather information for flying in Europe, including all airport notams, calculations, country information, airport webcams, FBO database, and all aviation abbreviations.
http://www.flyingineurope.be
Turbulence Forecast
Turbulence forecast maps for around the world.
http://www.turbulenceforecast.com
BalloonCast
Customized weather for balloon pilots. METARs, TAFs, winds aloft, sunrise/set for multiple stations compared side by side, all codes translated to English and times converted to local.
http://www.blastvalve.com/weather/
Aviation Weather
Displays live pilot reports, current and forecast weather (PIREPs, METARs, TAFs), temporary flight restrictions (TFRs) with optional radar overlays using Google maps.
http://maps.avnwx.com
Airwx Mobile
Get METARs, TAFs, PIREPs, and weather charts on your mobile phone (and iPhone).
http://m.airwx.com
Upper Midwest Aviation Weather
Central reference for aviation weather resources, focusing on current and forecast conditions in the upper midwest region of the US, including Minnesota, Wisconsin, South Dakota, North Dakota, and Iowa.
http://cloud7.org/um_weather/
Pilot Weather Briefing
Free weather information for pilots, including surface conditions, upper level winds, turbulence, icing, thunderstorms, TAFs and Metars, radar and satellite images.
http://www.pilotweatherbriefing.com
Meteo Mobile
Metar, Taf, satellite images, airport maps and nearby POI's delivered via mobile phone.
http://www.aviador.es/
