Led ring lights for 60mm f2.8

If you're looking for something very basic to experiment with and are willing to use manual exposure, you can get an LED ring flash on eBay or Amazon for ~$30.

Using it on my 20mm Panasonic lens for portraits at f5.6, the lighting is even and the color balance and recycle time very decent. I read that the flash duration is 1/100th of a sec, so a bit long to stop fast motion, but again, fine for my purposes.

You'd have to use manual exposure, since it has no Auto or TTL capabilities. It allows setting flash brightness and also allows using only half the LEDs for top or side-lighting effects. The description says that it can also be used for video as a continuous light source, but I have not tested this.

Model is RF-550D Macro LED Ring Flash.
eBay listing number: 300776097053

Another option that seems clever and allows the use of a TTL flash is called O-Flash - a ring that attached to an existing flash unit, guiding and distributing the light through a plastic unit that circles around the lens.