I came across a free chapter on basic PowerShell concepts in a recently published book about PowerShell. The book is Windows PowerShell Unleashed from Sams, written by Tyson Kopczynski, Pete Handley and Marco Shaw. The book, which focuses on PowerShell V1 covers the key aspects of PowerShell.
The free Online chapter is Chapter 2 which coves Basic PowerShell Concepts. While many readers of this blog understand PowerShell, re-reading a chapter on the basics is always good to reinforce our knowledge. The book itself looks a good introduction to PowerShell. I look forward to a new version of the book in due course, covering Version 2.