In a final meeting of scientists, engineers, technicians and officials, NASA's Gamma-ray Large Area Space Telescope (GLAST) received the final "Ready to Go!" from all teams. GLAST is scheduled to launch on a United Launch Alliance's Delta II Heavy rocket with a launch window from 11:45 a.m. - 1:40 p.m. EDT on Wednesday, June 11.
You can read more about GLAST at its official website. More info from Physics World can be found here.
Edit: Update - GLAST was successfully launched!
Photo credit: NASA/ULA