The USB powered Webstar II Light from Stellar Lighting Systems sells for about $50 and does a great job at helping to illuminate your face when web conferencing or if you are recording yourself using any type of application. It can be clipped onto your computer or mounted as a ring light to allow your camera to shoot through the middle.
The dimmer doesn’t work all that well but if you play around with it you can get several different values of light intensity. You can purchase directly from their website or through resellers like Amazon.com.