I've just discovered WalkIt, which I really like. Previously, I was using WalkJogRun, which I also liked, but had a slighly clunky interface where sometimes I was in the UK and sometimes I was in the US. But then, you can put in your weight, and it tells you how many personal calories you burn, which is nice. But because people can share your routes, I think they also can share your personal calories, and that's not so great.
Anyway, I'm walking to Kensal Green this afternoon, and that'll be my first test of WalkIt.