On the Wikipedia for Autodidacticism, there is a section labelled: Some notable autodidacts can be broadly grouped in the following interdisciplinary areas:

Artists & Authors

Actors, Musicians, and other artists

Architects

Engineers & Inventors

Scientists, Historians, & Educators

And, I have added (from my own research) Mathematicians, Philosophers, and anything having to do with Computers.

My friend has a website: http://www.autodidact.com/index/html and has written many books on the subject.