Make Flickr Pool member Latente illustrates the simplicity of building a ring flash using only a few simple parts.
Sharing photos of the creative process can be almost as satisfying as the finished project itself. But often lighting conditions in the workspace are less than ideal for photography. Ring flash units are great for providing even illumination and softening shadows in your photos – Build one yourself and up your maker karma to boot! – Link
Super-cheap, DIY ring flash –Link