Here's a link to an article from the B&H newsletter by Tom Kirkman on video lighting for interviews. While the lighting instruments he recommends are a bit pricey, cheaper lights may be substituted. Also the diagrams fail to indicate the position of the interviewer. Typically the interviewer is seated near the camera, between the camera and the main light (also referred to as the "key light").
Vortex Media also offers an excellent and affordable instructional DVD on video lighting, How To Setup, Light, & Shoot Great Looking Interviews (using a light kit that costs under $1500). You can check it out here.