Mouse Party is an awesome little animation that teaches the basics of the neuroscience of addiction. The animation is part of a set of educational resources on the science of addiction, which is itself one part of the broader Learn.Genetics site. (There is also Teach.Genetics website, but it's still in beta). By the way, the Inside a Cell animation, part of the Amazing Cells suite of materials, is pretty cool too.
All these resources were created by the NIH-funded Genetic Science Learning Center at the University of Utah.
(Hat tip: Hugh).