People concerned with their level of eco-cred often feel the urge to measure themselves against others. One-upmanship is the order of the day when environmentally-aware types get together. It is very important to always win these contests. If your buddy bikes to work every day, then tell him that you also bike to work, while charging your laptop using converted pedal-power. Having an iPod powered by solar cells is a nice touch, too.
Riding public transportation is a reasonable effort towards eco-credibility, but if you take the bus because you don’t feel like driving, don’t tell anyone…Make them think you refuse to use a pollution machine that contributes to gridlock, choosing instead to use your time on the bus to invent new uses for Hemp. Hopefully your fellow passengers will never notice that you drive an SUV.