Square Ring Light is a bit of an oxymoron I know....
but I promise I'm not just going crazy. See, the ring light is a type of light that is heavily used in macro photography, as it spreads a fairly soft light very evenly. Those qualities make it a good light for portraits as well.
The ring light has a very distinct look too it, especially when used head on. It wraps around the subject and gives a nice looking vignette, as well as a unique catchlight as in the image below.
But used off axis, it behaves almost like a small softbox. It delivers a very soft and pleasant light, as can be seen by these two pictures:
So the impressive thing here is not that you can use a ring light for portraits. That's well known. What is impressive, is that all of these photos were taken with a DIY ring light made with less than $10 worth of materials.
Impossible you say? Well my square ring light (square because its easier to build than a round one) cost me $8 dollars, plus some aluminum foil that I already had at my house. For the full specs, check out the original post at DIYPhotography.net.