I live in the typical old 'college' house. My roommates and I have a lot of energy wasting issues to deal with because of how old the house is and on a tight budget, these issues can become financial problems. The most prevalent during the school year is heat loss. Because we only live in the house during the school year, and we live in North Dakota, the months that we inhabit the house are obviously the coldest months of the year. An obvious way to reduce our heating bill is to use and lose less heat.
One step we took was putting up window plastic. This is a cheap way to make a noticeable improvement on the amount of heat you lose through your windows. Here is a starter kit from Walmart. This kit also includes outlet sealers and weather stripping for your door. Also, here is a short tutorial on how to install your window plastic.
Here are some other ideas from one of my favorite blogs, Savvy Housekeeping. My favorite ideas from her are getting a timer for your thermostat and to simply dress warmer.
Taking these small steps can have a large impact on what your heating bill will be. For me and my roommates, we have electric heat. Reducing the amount of time we have to run our furnace, has a major impact on how much electricity we use in a month. If we're using less electricity, our ecological footprint is shrinking right along with our electricity bill. If you have a natural gas, coal, or any other heater, you will also save money using these steps.