There is new legislation that is changing alot in the light bulb industry. In 2012 the 100 watt incandescent bulb will be phased out and then in 2013 the 75 watt bulb will follow and 40 watt and 60 watt will follow in 2014.
There is no requirement to replace your existing light bulbs but manufacturing of new incandescent bulbs will end. CFL bulbs are the common repalcement, althought LED and Halogen are other bulb options. CFL bulbs do cost more than incandescent bulbs but will save in the long run.
You can view the GE Lighting Website for more information.