Heavens-Above
This is a fun site to explore. Even if you're not into astronomy, you really should experience a good Iridium flare at least once. Just make sure that your watch is set correctly because they only last a few seconds at best. In order to calculate the flares, heavens-above will need fairly precise measurments of your lattitude, longitute, and elevation. You can use TerraServer to find your lattitude and longitude. The USGS will be happy to tell you the altitude of a nearby landmark.