Today at 4:50EST (1:30PST) the space shuttle Discovery will launch for the final time, delivering The Permanent Multi-Purpose Module (PMM) and spare parts to the space station.
The last flight for the Endeavor is planned for April 19th, 2011, carrying the EXPRESS Logistics Carrier 3 (ELC3) and the Alpha Magnetic Spectrometer (AMS).
The last flight of the Atlantis, and the last space shuttle flight for the space shuttle program, is planned for June 18, 2011 and will install the Multi-Purpose Logistics Module.
The first space shuttle took flight on April 12, 1981, and the last flight will occur just after 30 years of STS missions. With two million moving parts and 150 miles of internal wiring, the space shuttle is the most complex machine ever created.
wikipedia said:
The shuttle program is scheduled for mandatory retirement in 2011, in accord with the directives President George W. Bush issued in the Vision for Space Exploration. The shuttle's planned successor was to be Project Constellation with its Ares I and Ares V launch vehicles and the Orion Spacecraft; however, in early 2010 the Obama administration asked Congress to instead endorse a scaled-back plan with heavy reliance on the private sector.
While we can change personnel at the space station via the Soyuz spacecraft, and we can lift some smaller new modules and load into orbit, the space shuttle is the only means we have to launch very large items, and take nearly any medium to large items out of orbit and bring them back in one piece, as well as the only platform which allows us to service satellites, such as the Hubble Telescope.
Added at: 15:01
You can watch the launch preparations and launch on NASA TV:
http://www.nasa.gov/multimedia/nasatv/index.html