Christopher Jones and Daniel Kammen of U.C. Berkeley produced a very useful paper in 2011 that outlines ways for households and communities to lower their climate change impacts. A lot of good information is crammed into that report, but one of the most immediately helpful pieces is this graph:
From Jones & Kammen (2011), “Quantifying Carbon Footprint Reduction Opportunities for U.S. Households and Communities“
The height of each block in the graph shows how much money would be saved by that activity in a year, while the width shows how much it can reduce your carbon footprint. Jones and Kammen estimate the average footprint of an individual in the U.S. at about 20,000 k-coes/year (though there are different estimates from various sources based on different guidelines), or about 48,000 k-coes for a typical household.
If you can do a particular item more than the amount they use for their calculations, of course, your savings could be even bigger.
The authors have created a Web site called the CoolClimate network that offers free calculators for businesses and individuals to find ways to lower carbon footprint, along with other tools.