There's a lot of good info on spinning.com which is the Johnny G "aka Spinning" certification. Keiser Power Pacing was another cert I ran into but personally I though Johnny G was very well accepted everywhere.

You take a day course, in which you will also have a ride and learn class techniques. There is a test, and then after 3 months (I think that's what I remember) you'll receive your certification. You can teach prior to that point though.

Also try visiting the forum Pedal-on.com for more diverse thoughts on the matter...good luck!