This page has a portal through which you can view the current location of the International Space Station, updating in real-time. The tracker itself comes from the European Space Agency (ESA).
Part of the tool doesn't seem to be working properly yet, raising an error when the widget first loads. A possible explanation for the error is detailed below. There is also a handy link to get email notifications direct from NASA when the ISS is visible in your night sky.
When the widget has loaded (it may take a few seconds) you'll probably see an error from GoogleMaps in the lower portion. Just click that away and it won't bother you again (until you return to or refresh the page - such is life). I think it's probably a timing issue, with Google Maps being requested for data before the widget knows what data to send.
The yellow track is where the station has been and the white track is where it's going (hence the +1.5 h and -1.5 h labels). A single orbit takes approximately 92 minutes. If the station passes directly overhead at your location, and assuming you have no obstacles such as buildings or mountains blocking your view, the station will be visible for around 10 minutes.
The ISS is orbiting at approximately 27,600 km/h - 17,150 mph - and the orbit is inclined to the equator at 52°.