They'll be carrying a Russian mini-research module, batteries, a dish antenna and other replacement parts, along with an experiment to test how micro-gravity affects the growth of bacteria (and hence the space station's and crew's health).
This is supposed to be Atlantis's last mission before she's retired and it should be an exciting one,according to program manager John Shannon. Watch for three spacewalks and "tons of robotics."
Lift-off is scheduled for 2:20 p.m. Eastern Daylight Time. There's lots of information about the launch on NASA's Web site, and Smart Planet will be following it from Nasa Ames, which is providing live coverage.
See you there!