I recently downloaded a document called "Embedded Design Guide" by Tektronix. It's a 54pg PDF file that serves as an introduction to testing Embedded Systems. You can find it here or here.
My experience with embedded systems work is very limited, confined mostly to writing code for a microcontroller or debugging software written on an embedded system. But I like to have at least a passing familiarity with most technology I have to use. I haven't finished reading the file, but it appears to provide just that: a passing familiarity.