Divet has a nice Instructable on how-to make a ring light out of disposable cameras Looks like it works well, just watch where you put your fingers.
Build a disposable camera ring flash. Disposable cameras are discarded after the film has been removed. Photo labs often have boxes of them under the counter, waiting to be recycled. If you ask nicely, you can often get more than enough to experiment with. Try to get at least six for this project, all of the same type.
Disposable camera ring light – Link
Eye on Birmingham: The Ring – Link