The green movement is quite trendy today. Yet, many people have been living green for a long time, maybe without even realizing it. No matter the reason for "going green", green choices are often economical. A big (broad) example is that reducing one's consumption is probably one of the most environmentally-friendly things a person can do. Decrease your amount of consumption (of cars, clothes, energy, electronics, fuel, food, paper, plastic, toys, water, etc.) and you will inevitably save money as well.
Green (our environment) and green (your money) go hand in hand. "Going green" does not only mean buying expensive pairs of organic jeans (but props to you if you can afford them and want to spend your dough on them) or having the latest, coolest Hybrid. Driving a 1998 used-Honda that is well-maintained can be what makes sense for you. And it can be especially green if you are conscious about your driving habits (no quick starts or stops) and you try to lump trips together when you do drive (instead of walking, taking public transportation, or biking). Likewise, buying new (even if it supposed to be eco-friendly), while trashing something older, doesn't necessarily make sense, especially if the old goes directly to the landfill.
Being conscious and reducing what you consume are things that can easily earn you more green [since more green money (at least for those in the States) will remain in your savings account]. At the same time, you are being "greener" and more eco-savvy.
For more thoughts on being a clean, green machine: