A new option to light the way, even as 100-watt bulbs disappear from stores because they were energy hogs? You can now get LED bulbs that roughly match the 100-watters for size and brightness, but use far less energy.
Until recently, your only alternative was a compact fluorescent bulb, which has several drawbacks compared with light-emitting diodes. Most people see the light quality as less pleasing, and the bulbs contain a small amount of mercury that's released if the glass breaks. LEDs, by contrast, don't contain any volatile, hazardous substances and are durable. They also last longer.