One of the things I've been remiss in not mentioning is CWLP's enhanced energy efficiency rebates. You may recall that as part of the Sierra Club agreement, CWLP is increasing its spending on energy efficiency programs from $40,000 per year to $400,000 per year. They're going to be conducting a study to see how best to use that money; in the interim, however, they're supercharging their existing insulation rebate program, offering to cover 30% of the cost, up to $500. Insulation is always the place the start when you're looking at your home energy use.
And if you're not sure where to begin, consider either getting a home energy audit, where someone will come out and go through your house with you, helping you to prioritize what you can do to lower your energy use, or attending a low cost/no cost workshop, which gives you insight and experience in plugging all the little gaps in your home.