Esri Press has released a new book called The GIS Guide to Public Domain Data:
[The book] provides GIS users with detailed information about the sources and quality of spatial data available in the public domain and the policies that govern its use.
This guide covers practical issues such as copyrights, cloud computing, online data portals, volunteered geographic information, and international data. It provides GIS practitioners and instructors with the essential skills to find, acquire, format, and analyze public domain spatial data. Supplementary exercises are available online to help put the concepts into practice.