The Space Shuttle Discovery is set to deliver the power-generating solar panels and Starboard 6 (S6) truss segment (the final piece of the station's backbone) to the ISS on the 125th mission in the Shuttle program, known as STS-119/15A (slated for launch on March 11, 2009 at 9:20 p.m. Eastern).
Once these components are installed, the ISS will become the second brightest object in the night sky, brighter than Venus, and second only to the moon.
You can go here:
http://spaceflight.nasa.gov/realdata/sightings/
for information about where and when to see the ISS fly overhead. It's quite a sight now, sweeping from horizon to horizon in just a few minutes, and it will be really spectacular in a few weeks. Show it to your kids.