A good friend of mine alerted me to this wonderful article about how to find and implement the “low hanging fruit” of being green. There are some excellent resources throughout the article and within the comments. Be sure to read through them as there are links to websites with more details on programs available to the public.
In particular, there is a guy who even gives his thoughts of the small steps he could take (and did) while being a renter. You don’t have to own to help make your home more efficient. In fact, in many cases it will be to your benefit since many landlords have the tenants paying for their own utilities.