A decade ago, the Rocky Mountain Institute released Cool Citizens: Everyday Solutions to Climate Change: Household Solutions. It was full of great tips for what you can do to reduce your energy use. However I found the most important feature was this page, which ranked measures you can take by the bang for the buck. It was pretty shocking, demonstrating that we have been pretty much sold a bill of goods, of expensive green gizmos, that cost a fortune in proportion to the money and carbon they save; a programmable thermostat saves more than changing all your windows. Insulating your ducts saves more than an entire solar hot water system.
Much has changed in a decade; fuel costs more and energy saving light bulbs cost less. Few of the numbers would be accurate now but the order of things won't have changed much.