Not the most beautiful park in London, but certainly one of the most expansive. Clapham is a great place to play sport and also a nice
place to lounge around, drink beer and sunbathe on warm summer days. There's a bunch of organized sport on clapham common (particularly between April and September). Everything from Softball & Tennis to Touch Rugby & Ultimate Frisbee. Best to look on Gumtree if you want to join a sports team in this area.
Clapham Common also plays host to a bunch of festivals and concerts all year round. The Ben & Jerry's festival is worth a go.
SPORTS TIP - Booking a tennis court on clapham common always seems really difficult. Best to head down to the courts after 7pm and book for the following weeks or months if you are a tennis enthusiast!