Incredibly, there is a light bulb in Livermore, California that has been burning since 1901. The aptly named Centennial Light serves as a nightlight for the firetrucks of the Livermore Fire Department. There is a live webcam on the official website of the Centennial Light. It has been declared the oldest known working lightbulb by Guinness Book of World Records.

The Shelby Electric Company made the bulb. It was handblown and then outfitted with a carbon filament. It has about 4 watts of light.

If you happen to be in Livermore, California then you can stop in and visit the bulb, depending on the availability of the firemen. If you go to the rear of the station and ring a bell then you can ask them to let you in. Otherwise, according to their site, "you can see the bulb if you look through the window up on the top of the wall to your left." The photo below is courtesy of the Centennial Light Bulb Committee. There are more of photos to be found here.