NASA - Spot The Station is a site where you can sign up for email and text alerts when the ISS is above you.
NASA’s Spot the Station service sends you an email or text message a few hours before the space station passes over your house. The space station looks like a fast-moving plane in the sky, though one with people living and working aboard it more than 200 miles above the ground. It is best viewed on clear nights. For more information on the International Space Station and its mission, visit the space station mission pages.