I just added "A Guide To Open Content Licences" by Lawrence Liang to my 'basics' section.
The book tries to answer some questions, like:
What is copyright?
What is copyleft?
How can we share culture in a world where everything has a license?
"Scientists, writers, designers, artists, musicians and others are increasingly interested in making their work available in 'the public domain'. This booklet is an overview of the ways in which this has been done and a guide to the growing area of Open Content Licenses through which people design and safeguard access to their work."
You can download the guide here (pdf). Thanks to Peter from Constant.