The best sports that London is good at is cricket and swimming.
26 olympic sports and 20 paralympic sports will feature at the London 2012 Olympic and Paralympic games.
Bit of a vague question, I'll give it my best shot though... Football (Soccer), Rugby, Cricket are some of the more English of sports in London, but it's a huge city, practically all sports and games are played there
cricket
rugby
26 sports and 39 disciplines
Football, Rugby, Snooker, Darts
soccer
cricket
26 sports and 39 disciplines
which weekend?
Chelsea in reference to Barcelona sports is a F.C. team from Chelsea in central London. Chelsea is a very prominent team and is considered one of the best and hardest to beat.
26 Olympic sports, and 39 disciplines, in London 2012 Olympics - for Paralympics, it's 20 Sports in 21 disciplines. Source - London 2012 GamesMaker handbook.