My wife and I have been talking about this a lot. Where we live, making a political difference is pretty impossible...I'm in most of the most democratic congressional districts in the country, and we'll only have meaningful elections at the city or state level once or twice a decade.
This is what we do now. We'd like to do more and are talking about other ways we can best deploy our time.
1) We've become pretty waste conscious about food. We usually grocery shop at bulk type co-ops so we can avoid using as much packaging, and if it isn't bone-chilling cold, we'll walk or take the train to the store. We have reusable bags and bring tupperwares to the deli to so we dont need to waste another plastic bag. We also compost. We also don't buy meat very often at the grocery store, and when we do, it's usually white meat or fish.
2) We use a cloth diaper service instead of disposables (which would easily be our biggest source of waste).
3) We give to a variety of charities, including our church, planned parenthood, the ACLU, mico-loans in the developing world, and local food banks.
4) We are volunteers for our neighborhood park.
5) We spent the first five years of our marriage without a car. Outside of taking my children to day care, and running errands when it is REALLY cold, I don't use it very much. I work from home and prefer walking when I can.
If we can find time, I'd like to actually volunteer at the food bank, and hopefully be involved in a more meaningful way in this mayoral election, or other neighborhood groups. It sucks that more meaningful political participation, if you don't live somewhere where those elections matter, depends on how much money you have.