There are a variety of weather-related websites useful for sailors, and just as many distinct forecasts. Here are a few we like:
Sailflow.com - Fairly accurate aggregate of several forecast models. Shows wind direction, speed, and air temperature. Link goes to Lake Travis forecast.
NOAA - A good combination of wind, temperature, and precipitation forecasts in a nice graphical format. You can also click on the graphs for text, if that makes things easier.
Wunderground.com - Not generally used for wind forecasting, but useful for cloud cover and precipitation forecasts... a must when deciding what to wear! Link goes to Austin Yacht Club zip code forecast.
Austinyachtclub.org - Weather station right on the lake tailored to sailors with current conditions and historical data. There is also a handy utility you can add to your Windows system tray for real-time updates.
ARL Lake Travis Test Station - The UT Applied Research Labs sonar test station maintains a website for Lake Travis conditions at the South end of the lake, and of particular utility is the water temperature data. Also very important when determining what to wear.
Weather Spark - WeatherSpark is a new type of weather website, with interactive weather graphs that allow you to pan and zoom through the entire history of any weather station on earth.