The Commonwealth of Learning has published Introducing Copyright: A Plain Language Guide to Copyright in the 21st Century as a PDF file under a Creative Commons Attribution-Noncommercial-No Derivative Works license.
Here's an excerpt from the announcement:
This book was written for those who want to learn about copyright in the 21st century. It explains copyright protection and what it means for copyright holders and copyright users. It also introduces readers to contemporary topics: digital rights management, open licences, software patents and copyright protection for works of traditional knowledge. A final chapter tries to predict how technology will change the publishing and entertainment industries that depend on copyright.
The book assumes no special knowledge and avoids technical language as much as possible.