The London Pass gives free entry to more than 60 attractions, including such star turns as the Tower of London, London Zoo, St Paul's and Hampton Court, as well as free tours (including a Thames river cruise and canal trips). Lesser known, but equally worthy, attractions are also included: the London Wetland Centre, Pollock's Toy Museum and the Benjamin Franklin House, for instance. At some busier attractions, you also get to skip the ticket queues.
A 160pp guidebook (choose from seven languages) is included, you can download a tailor-made app, and there are shopping and restaurant discounts and benefits. There's also the option to pay a bit more to add in a slightly reduced travelcard for each day.
It is worth remembering that entry to many London attractions – among them Tate Modern, the British Museum and the National Gallery – is already free, so do some research on the places you plan to visit in advance.
Note: under-11s travel free on the tube, buses, DLR and Overground if accompanied by an adult. You'll pay at least £2.95 more to have the card posted to you, so consider picking it up in person at the address given.