one idea i had recently for my sabbatical projects was to design a website with a social component that would allow people to input bike trips they've made and see how much gas, money, and emissions they've saved, as well as add up miles and calories burned. then you could share that info on FB and twitter. there could even be a challenge component to it, allowing friends, groups, or even cities to compete against each other. the point of it is to encourage people to use bikes for various trips (commuting, eating out, small errands, visiting friends) rather than cars.