The Space Shuttle Discovery launched successfully yesterday, and it's on its way to the International Space Station. It will dock with ISS tomorrow, April 7.
Until then, the Orbiter has to play catch up, slowly changing its orbit until it matches the station's. The thing is, you may be able to watch this unfold! Both the Orbiter and the ISS are easily visible to the unaided eye, and in fact the station is potentially the fourth brightest object in the sky (after the Sun, Moon, and Venus). As they approach each other, you can see them as bright(ish) stars moving rapidly across the sky.
You can find out if they are visible to you by going to a site like Heavens-Above. Enter your latitude and longitude (try Google maps to get that) and it will put you on a page that gives you times, directions, and brightnesses (in magnitudes, so a more negative number is brighter) of a lot of different satellites. Click on ISS or STS-131 to get the station or Orbiter times.
All the good passes for the next week in Boulder, for example, are in the early morning. I suspect I'll miss them. But check your local times and see if you can catch them! It's an amazing sight. The picture here is one I took myself using nothing more than a digital camera on a tripod -- click to embiggen it. It shows a time exposure of Atlantis and the ISS from 2007, and you can see how they are on very slightly different orbits. The two were separated by a small amount; you can tell by the different end points of the trails.
There aren't many Shuttle flights left, so get out there and observe this while you can!