Understanding Optical Slaves
David Hobby over at the Strobist has an excellent article on optical slaves. Here's the lead to the article and a link at the bottom to read the whole piece:
Understanding and Using Optical Slaves, Pt. 1

First off, this is a long-overdue post. It arguably could have been in Lighting 101. But this week (four-plus years later) we'll be looking at choosing and using optical slaves. In this post, how to figure out which kind is right for you.

