I bought the ring light off amazon ages ago, it works well, but if using for macro and you get too close the light level falls off, but saying that I was still getting enough light when the the subject was 2 cm from the lens.
If you are shooting people it is a bit to bright for your subject to look directly at the camera - I spotted a LED system on the interwebs (but lost the link of course

) that works like a flash ring triggered off the hotshoe, looks good, then there are huge contraptions that attach to the lens that direct the on-camera flash into a ring light.