A great place to start the day if you are in South London is Federation Coffee in Brixton Village. The food is great and so is the coffee. This is a very chilled place where you can get both and indoor and outdoor experience (even though the whole place is under the Village roof).
Slightly biased as this is where I live, but Stoke Newington is great place to spend lazy saturday / sunday afternoons getting sloshed with friends. There are 10 + pubs within walking distance who all are great places for one reason or another. I'll pick out the White Hart for its huge beer garden...
Hidden away in the backstreets of Finsbury Park, I used to share a house opposite this pub, where it assumed the role as our second living room. A real north London gem, I still go there these days for the tree-house-like, leafy terraced beer garden, which is perfect for summer evenings.