The Space Shuttle Discovery will be launching for the last time on February 24th at 1:50pm PST. Mission STS-133 will be the 39th flight of the 27 year-old spacecraft, and will be bringing the Permanent Multipurpose Module Leonardo to the International Space Station, as well as the Robonaut 2 robotic astronaut helper.
With only two more Space Shuttle flights scheduled (Endeavour in April and Atlantis in June), this represents the end of an era of ambitious human space exploration, as after that the US will be left with no means of sending astronauts into space and will rely on Russian Soyuz spacecraft to reach the ISS.
With the cancellation of the Constellation moon program in October 2010, the only serious prospect for US manned space flights is the privately funded and operated Dragon capsule from SpaceX, which, although a remarkable achievement for a private company, is a return to 1970's designs, and is nowhere as advanced and capable as the Space Shuttle. And Dragon will not be operational before 2013 at the earliest.
Watch the historic flight live in HD on ustream TV.
Update: For those who missed it, here is the video of the launch.