London Busses
Those large, red double-decker busses are as familiar as a London icon as Big Ben or the guards at Buckingham Palace. They are a great way to get around the city and unlike the "tube" (subway) they provide a great view along the way. One day passes can be purchased inexpensively and maps are readily available displaying routes to various locations.

Another alternative is to take advantage of some of the tour bus companies that operate in the city. Open on top and enclosed from the weather on the bottom, these busses have tour guides that point out the sites, explain history and answer questions as you move through the city. Most of them allow you to disembark at the major attractions and then catch a later bus whenever you are ready to continue your tour. Information on two of the major operators in the city can be found at The Original Tour London and the Big Bus London.