Here is a review of powerful on-camera LED lights from Celadon.

We used these lights when doing interviews at the NAB Show this year, and they were definitely helpful.

Tom recently reviewed the AL-M9 light from Aputure. In contrast to the Celadon lights, the Aputure on-camera light is very light, but also much less powerful.

You can buy the Celadon lights here:

Radiant 2XL Pro 160 SMD LED Bi-color on-camera light on Amazon, eBay, Celadon website

Radiant 2XL 280 LED Bi-color on-camera light on Amazon, eBay, Celadon website