Thomas Edison presented his first light bulb in 1879 (U.S. Patent 223,898 - there were many disputes about this*) and it's been improved upon and made more efficient ever since. But while the efficiency is welcome, there are now beautiful reproductions - called Edison Bulbs - that are perfect for some decorative uses and low light areas...
For example, the lamp above I saw in the window of Michele Varian this morning. The bulb has a cool effect in that you can look right at it and see the fragile filament without hurting your eyes. The best feature is the simple loops of filament. There were (and are) a lot of styles, and some are still made with carbon filaments (Edison's was a bamboo filament).
I use these with vintage lamps and have seen them used to great effect in bars and restaurants where they add a low warm glow and a vintage feeling. Because of their old fashioned construction, they are NOT efficient and you should know that up front. They can put out 25 watts of light while using 60 watts of electricity, but used sparingly that shouldn't be a big deal.
I put together a list of sources as well as the history of these bulbs down below. Check them out. If you ever want to spiff up an old lamp or do something special where changing the light bulb is your only solution, this is a great arrow in your design quiver.
EDISON BULB LINKS
>> Edisonian.com - history and intrigue surrounding the patent*
>> Wkipedia Entry - Incandescent Bulb - full history*
>> CoolQuiz.com - short answer of the patent dispute*
>> Rejuvenation Lighting - source
>> Destination Lighting - source
>> Van Dykes - source
>> House of Antique Hardware - source(ReEdited from 2008-02-06 - MGR)