For those of you in the upper midwest, the International Space Station and Space Shuttle Endeavour will be visible tonight. Provided there are no clouds, you'll be able to see them pass from west to east in the northern sky on a line that will pass between the horizon and the north star, Polaris.
This mission for Endeavour is called STS-127. They are connecting another module to the International Space Station. There are currently 13 people on ISS so be sure to wave as they fly by.
For us here in Minnesota, the ISS and Shuttle will be visible beginning at 9:47pm CDT through 9:57pm CDT. The ISS and Shuttle make one complete orbit around earth in about 90 minutes. That's about 17,500 miles per hour relative to us.
It looks like the next pass begins at 11:22pm CDT to 11:33pm CDT. This pass will appear to go straight up beginning from North West horizon and will proceed towards the end of the handle on the Big Dipper.
Go to NASA's Human Space Flight (HSF) Realtime Data site to plug in your location and search for your own sightings.