Pay $3.19: Take Public Transportation

By one estimate, the public transportation system in the United States saves 3.4 billion gallons of oil a year (and cuts greenhouse gas emissions by 26 million tons).

Get your fair share of the savings by looking up the local bus route or climbing on the subway. (After all, as a taxpayer, you've already invested in the service.)

Sure, it costs money to take the bus or subway. But consider this: The average U.S. commute is 16 miles, and at these prices the average U.S. passenger costs $2.26 to go 16 miles ($2.80 for an SUV), and that's roughly the cost of a typical public transit fare. It's a wash.

Plus, you'll save wear and tear on your car, a hefty hidden cost of driving.