One of the problems with suggesting ways to drop one's energy bill is that the savings are generally small and incremental. Consequently, many money-saving methods can end up costing you more (at least in the first year) than they save.
That having been said, there are many reasons to invest a little bit of money in one's abode. First off, if you own your home, or plan on renting it for a few years, the initial expenditure will pay off much larger dividends over time. Second, plugging up leaks and insulating your space decreases drafts and hot water outages, greatly improving the quality of your life. If you've ever been awakened by your own shivering, ran out of hot water in the middle of a shower, or found yourself swearing at your utility bills, then you know what I'm talking about.
Without any further ado, here are a few simple (and relatively inexpensive) ways to reduce your utility bills:
Insulate Your Water Heater
Okay, I can't stress this one enough. If your water heater feels hot to the touch, then you are throwing away money. Most home repair places sell water heater blankets for $10-15. These are, essentially, sheets of plastic-backed insulation that you duct tape around your water heater. It takes about twenty minutes to do, and will save you about...you guessed it, $10-15 per year. However, you only have to insulate the heater once, and the savings will accumulate for as long as you live in your home.
Incidentally, if your hot-water pipes run through a cold basement, then you are also losing energy there. Pipe insulation isn't too expensive, and will ensure that the water you're paying to heat stays hot. You'll find this particularly wonderful when your hot shower lasts for an extra couple of minutes!
Seal Air Leaks
Caulking, silicone insulation, and foam insulation are all pretty cheap, but sealing the large leaks around doorways and windows will save you a ton of money. This one's pretty simple. If you can feel a draft, chances are that your window sill or door frame is leaky. According to some sites, closing off these drafts can reduce your electric bill by as much as $80 per year.
Unfortunately, I've found that caulking is a job for warmer weather. In the dead of winter, the caulk might not cure properly. If it's too late in the season to do your caulking outdoors, consider shrink-wrapping your windows. Most DIY centers carry window-wrapping kits, which make it easy to create an insulating air barrier in your window. This will reduce drafts, massively drop your heating bill, and generally make your home a warmer, fuzzier place to be.
Efficient Shower Heads
Seinfeld once had a low-flow showerhead episode. Basically, Seinfeld's landlord secretly replaced all the showerheads in the building, which led to insufficient rinsing, greasy hair, and all sorts of misery.
Watching the episode, I completely understood. Personally, I go back and forth between soft, relaxing showers and powerful, tearing-your-skin-off, monster showers. When the water pressure is too low, I resort to all sorts of byzantine solutions -- covering up holes, bending the hose, and so forth. That having been said, it is, indeed, possible to have a low-flow shower with a great deal of water pressure. The solution is finding one that properly aerates your water. Personally, I have a low-flow Waterpik showerhead that gives me the option of a high or low pressure stream. It's made me very, very happy.
The savings from low-flow showerheads are nominal. While you will probably shave about $20 per year off your water bill, the showerheads will run you at least that much. However, since a good showerhead will last for years, you should be able to enjoy the savings for quite some time. Besides that, you may discover that you enjoy the comfort of a specialized shower: I liked mine so much that I took it with me when I moved!