Strength and Flexibility Assessments

Can someone recommend a good source (book, site, video, etc.) on performing and interpreting strength and flexibility assessments?

I've heard NASM has some good stuff, but would like some other opinions.

I have a good book on muscular flexibility and posture assessment called “Muscles Testing and Function by Kendall and McCreary” The book has more then enough illustrated and easily understandable tests to keep you occupied with.