Sean Sullivan over at Brendan Loy’s The Irish Trojan reports that the Shuttle Endeavour will be visible, for a brief period, in much of the United States tonight:
The space shuttle Endeavour will be visible tonight from much of the United States, as the shuttle prepares for landing Tuesday afternoon at the Kennedy Space Center. This is a somewhat rare opportunity, in part because the shuttle spends most of its time in orbit docked to the Space Station, and in part because the orbital alignment needs to be right for bringing the shuttle overhead shortly after sunset or before sunrise. But these conditions are met tonight – the two are presently undocked, so they can be seen separately as bright stars moving across the night sky; and the orbital alignment is bringing these objects over the United States shortly after sunset.
To get the exact time (and place in the sky) for your location, try orbital predictions at Heavens Above. Choose your geographic location, then click on 10-day predictions for ISS (space station), and look for a pass on the evening of the 20th (tonight). Shuttle and station will follow the same track across the sky, probably within 1 minute of each other. Both objects will be similar in brightness to Jupiter or Venus – meaning they’ll be easily visible to the unaided eye, even from the middle of a big city. The visiblity will be short, however, usually about two minutes total duration. I don’t know for sure which is which – I’ve seen conflicting reports about which object is leading at the moment.
Unfortunately, it looks like cloud cover here in Northern Virginia will prevent me from seeing anything.

For what it’s worth… we saw two satellites tracking very fast in the same orbit Sunday night just after sunset (in Casper, Wyoming). Husband, the pilot, identified them correctly as the ISS and STS-118! Wife, the grad student, did some online research and verified that that is exactly what we saw, and that we could view it again Monday, August 21st.
We gathered our two teenagers (17 & 14) and another friend (18) to watch it happen again! Even they were impressed! Ignite the imagination and who know what will come forth? Thanks.