You can buy them at the London 2012 Shop. The official poster costs £7, and there is a wide range of other products you can buy there too, such as a poster showing the history of the Games or a poster showing the two Olympic and Paralympic mascots, Wenlock and Mandeville. You can also buy things like commemorative glassware, cushions etc, which might make nice presents for someone who really enjoyed the Games - plus Tshirts and other clothing.

There is even a full exhibition of all the Olympic and Paralympic posters at the Tate Britain Gallery running until September. It looks as if people still haven't had enough of the Games - all this memorabilia is still selling, and lots of clubs, restaurants, dance venues etc are still doing Olympic themed evenings even now the Games are finished.