London Bus Transportation
There are weekly and monthly passes good for unlimited travel on all London buses, but a better deal is the London Travelcard, good for unlimited travel on both the Underground and the buses. Travelcards can be purchased for 7 days or more at a time, but they require a passport sized photo.
Visitorcards are another option. They do not require a photo, and can only be purchased outside the UK. In addition to unlimited bus and Underground travel they include discount vouchers for many popular tourist attractions. Note that the Visitorcard is NOT valid for the Heathrow Express.
Take a good look at the zones on a transport map (available free at any tube station or at the London Transport web site). Most of the major tourist attractions are located in Zone 1, so you're fairly safe with a Zone 1 or a Zone 1-2 card. However, be sure to check the location of your hotel against the fare zone map. If your hotel is out in zone 6 and you will be traveling to Inner London, you'll need an all-Zone Travelcard.
Adult Zone 1
Adult Zone 1-6 (ALL-Zone)
Zone 1- 2
London buses can provide a good orientation for first-time tourists. Several routes in particular connect popular travel destinations.
Route 11 begins at Liverpool Street Station and passes St. Paul's before traveling along Fleet Street and The Strand to Trafalgar Square. Then it swings through Westminster and posh Sloane Square before taking in King's Road.
Route 14 starts in Riverside-Pulteney, before traversing Fulham Road, South Kensington, Knightsbridge, Hyde Park, Piccadilly Circus, Leicester Square, and Soho.
Route 24 begins at Hampstead Heath, and travels through Camden and Tottenham Court Road to Charing Cross Road, Leicester Square, and Trafalgar Square. From there it goes through Whitehall, past Westminster Abbey to Victoria Station and on to Pimlico.
London Transport has wisely introduced night buses (marked with an 'N' on bus signs), which cover the late night time period when there is no underground service. Night buses begin service about 11:30 and run until about 6AM.