I've lived in Brixton, London for about five years, so I know the place pretty well. I also spend a lot of time drinking in Shoreditch, which isn't as poncy as it sounds. I think I know London reasonably well, so I've emitted a few pearls of wisdom on to this site. There's still a hell of a lot of work to do before it becomes a reliable guide, but hopefully more helpful people will get onto it soon.
The London Underground can be a overwhelming at first, and it's difficult to see what kind of area you will find when you come blinking out in the daylight.
Below is a set of links from each tube station to the nearest area article on Wikitravel. The assumption is the station will be in the area or a five minute walk away, anything longer will be stated. Unforunately there will be a lot of deadends, but hopefully these will be filled in time (by locals).