This article is from the Car Audio FAQ, by Ian D. Bjorhovde (firstname.lastname@example.org) with numerous contributions by others.
The best way to get the most current list is to call either of the
sanctioning bodies (IASCA or USAC). They can be reached at
602/437-4678 or 601/939-7828, respectively. You can also visit the
Official IASCA and USAC pages on the web at the following URLs:
IASCA - <http://www.iasca.com>
USAC - <http://www.soundoff.org>