Of course, the old standards, ie the tower of london, Windsor Castle, Hampton Court are great too. London is a great city. There were a lot of improvements along the Thames that were done in conjunction with the Olympics. The walkway along the riverfront is very nice. There are a lot of boats that have been turned into nightclubs and restaurants. I just got back a week ago from a five day trip.
Instead of getting an Oyster card from the Underground, get a seven day travel card from National Rail. (as an example, there is a ticketing agent at Victoria Station) You need to bring a passport size photo with you. You will get an ID card and a paper pass. The pass gets you unlimited travel on the underground and busses. The advantage to getting a seven day travel card from the National Rail ticket agent is that you can request a voucher for 2 or 1 admissions to all of the major sites in the city. You will save a great deal of money. While you don't need the pass for 7 days, you will more than make up for the cost with the reduction in the admissions. I paid approx 22 pounds for a 7 day pass for zones 1 and 2 which covers all the major areas in London. The admission for one person for The Tower of London is 16 pounds. Do the math. We ate at pubs for dinner, although I can't remember specific names off the top of my head. There are a lot of very nice eateries in Kensington. The food options have improved greatly. Go on Trip Advisor for restauarant recommendations in the areas you will be visiting or just wing it like we did.
Have a GREAT time. London is a fantastic city!