There are two shuttles on the pad at Cape Canaveral right now. Atlantis is scheduled to do some maintenance on the Hubble Space Telescope October 10, and Endeavour will be prepped for a possible rescue mission should something go wrong (Hubble is in a much higher orbit — 590km vs 340km, with of course a completely different inclination — than the International Space Station, where stranded astronauts could hang out for a while in the case of emergency). Sounds like a job for Blackstar from the West Wing universe…

If all goes well with the Hubble mission, then Endeavour will fly the usual supply trip to the station.