hey mvkath, you wanted to know what to do in london? I would recommend doing an opentop bus tour, touristy i know, but it's a great way to get an idea of the city. What do you like to do, museums, shop? Even if you don't like to shop you should definitely go to Harrods, it's in knightsbridge and is really easy to get to on the tube. it has it's own stop! if my memory serves me corectely it's on the picaddilly line. You should get a packed lunch from the food hall and take it to hyde park to eat! also you should try and visit buckingham palace, sometimes it is open to the public, you have to buy a ticket, i don't know if you can do this on the internet. There are lots of great are galleries if this is your thing. Visit leicester square, this is where films get their premiare (sp) and walk throught to china town, lots of good food! then you can also visit piccadilly circus (at night when it's all lit up is the best time to go). Covent garden is nice to visit for shopping and to see the street peformers. If you like to visit gardens you could catch the train to Kew. Greenwich is a great place to visit, ever fancied standing across a time zone, well this is the place to do it! You can also found out about Great Britains maritime history at the maritime museum. You can find out loads of info on www.visitlondon.com
I would recommend buying a day/weekly rover for the underground, but try and plan which zones you will be using before you buy it! London is split into zones and the tube is priced for each zone 1-6.
i hope this helps