I am a huge DIY enthusiast and I have made a lot of light modifiers over the years. About a month ago i made my own DIY ringflash. I was wanting to document it but i got distracted. Low and behold over at http://www.unplggd.com there is a post with some instructions on how to make one. Its not the same way i made mine but it is still another very effective set up. Mine is also a lot bigger which would soften the light a wee bit more.
Follow this link and go check it out.