Space Shuttle Endeavour launches tonight or early tomorrow morning, depending on what time zone you live in. The launch is scheduled for 2:28 AM EDT (1:28 AM here in the Central time zone) which means this will be the first launch in quite a while I have not watched live online.
This is a major mission, the longest duration flight to the ISS so far at 16 days. Over the course of the mission, the Japanese Kibo laboratory module will be added to the space station, along with a newer, improved robotic arm system (with two arms and fine manipulator "hands") from the Canadian Space Agency.
Additionally, Endeavour will be delivering Garrett Reisman for a stay aboard the ISS as part of Expedition 16 and will bring European astronaut Leopold Eyharts home from the space station.
Forecasters are projecting a ninety percent chance of good weather, and no problems have been indicated as of now, nine hours before the launch.