We use a couple of these:
http://www.coollights.biz/clled600-panel-dimmable-p-114.html
You can buy the battery plate add-on and power them off of a V-lock or AB gold mount, and they last a few hours at full intensity with one battery. Dimmable, and you can drop in a CTO panel to switch between daylight and tungsten (although it cuts a stop). You can also pick up the softbox attachment for $99, which is actually pretty good. Also check out the smaller LED they have - you could easily mount it atop the camera and power it off another battery.
I'm also in agreement with Ken - remember monkey in the middle - when shooting interviews, your subject is looking at your interviewer, who is standing between the camera op and the light.
Tom Nelson
Videographer/Editor
Essex Television Group
