Well, I came across this link in the Lighting forum: DIY Ring Flash So I decided to make my own. I didn't follow his instructions to the "T" but the result is just about the same. Diagram and BOM here: Parts List
Sorry about the volume of images, but it should help explain the "cause and effect".
This is a great thread, with lots of useful ideas. Here's my meagre contribution, built just last night. Background: the E-3 with Sigma 150mm and FL-50, just to give an idea of the size and distances involved. Since the Sigma 150mm has a working distance of about 15cm from the front element, I figure I want the light to begin focusing down just around the end of the lens.
I built the snoot out of thin corrugated cardboard that I salvaged from a box for an electric house fan I bought a few days ago. I selected this material since it was handy, nice and rugged, easy to form, and it had a kind of plasticized finish on the outside that should help preserve it a bit better.
