For me, I think traffic lights are the best situation of this. Of course, on the highway I try to drive at a higher speed - if I'm driving 200 + miles, cutting down to 50-60 can add the best part of an extra hour.
Although I do like it when I spot a fellow eco-miler
Always nice to see drivers get annoyed by more than one of us, only to have to brake/start their car at a red light.