What's a Scoville?
Capsaicinoid content is measured in parts per million. These parts per million are converted into Scoville heat units, the industry standard for measuring a pepper's punch. One part per million is equivalent to 15 Scoville units. Bell peppers have a value of zero Scoville units, whereas habanero -- some of the hottest peppers--register a blistering 200,000 to 300,000. Pure capsaicin has a Scoville heat unit score of 16 million." (p.140)
From Margen, S. et. al (1992).The wellness encyclopedia of food and nutrition: How to buy, store, and prepare every variety of fresh food. Distributed by Random House. ISBN 0-929661-03-6.
More Chile Links
Sources
Chileplanet.eu - Exhaustive list of chiles with descriptions, heat ratings.
CayenneDiane - Large list of chiles with average Scoville heat units.