I consider myself to be pretty environmentally friendly.. Not because of global warming theories or carbon footprint scams, but just because it's the right thing to be.
However, if you have disposable income and would REALLY like to contribute to a cause that helps the environment, I will have a website for you at the end of this message.
I work for NM State Forestry and we promote a lot of green agendas, such as forest thinning, which improves our forest and watershed health. New Mexico has far too many trees for the amount of water we receive in our forested areas, so this thinning will reduce the severity of catastrophic wildfires, thus reducing pollution.
We plant trees where needed and sell low cost seedlings to landowners who then in turn, use them to create windbreaks, which protect crops, stop erosion and lower home and structure energy costs.
At home, we recycle paper, plastic and aluminium. We really don't drink sodas much anymore, so the cans aren't a big problem. I still get plastic bags at the market, but we resuse them for other things.
When appropriate, we reuse the plastic containers that some foods are packaged in.
Lights off and water shut off while brushing teeth, of course. I only water the (small) lawn and other plants a couple times a week.
Could we do more? probably, but it's better than we were doing 5 years ago.
As for contributing to the environment... Every single penny donated to the New Mexico State Forestry Re-Leaf program goes into planting trees. There are NO overhead costs and no taxpayer dollars are spent. We grant up to $6k to $8k per project per year to plant trees on public property such as parks, school yards, solid waste disposal properties, etc.. The trees are bought locally and the grantees must provide accounting and maintenance for the projects for five years. I would imagine mosts state's forestry divisions or forestry commissions have a similar program. A lot of people donate as a way to ensure that they are offsetting their carbon footprint without most of the money going to overhead costs.
For more information -
New Mexico Forest Re-Leaf