Learn Powershell in a Month of Lunches by Don Jones and Jeffery Hicks is a good a book for the beginner. The book teaches a "think in Powershell" approach with small lessons. There's a also a free lab manual and slide deck which can be used to teach a class. I've used the book and material to teach a 3-day internal class on Powershell and recommend it to others seeking to provide low cost training to their co-works.