Film Source LA have posted up a few useful tools for filmmaking for your computer. These work on Dashboard on a mac, tho PC equivalents can probably be found.
Sun Position - which lets you input any location, time and date and kicks out the suns position.
Weatherbug - a pretty comprehensive weather widget with windspeed and access to local webcams to take a quick look.
Film Calculator Widget - they designed this so you can input footage-frame rate-film type and amount of tape needed.