The University of Chicago has made a three volumes of an on-going set on the history of cartography open access. I can't judge how good it is and haven't done much more than paging through it for a half hour, but it looks interesting.
About The Project
The History of Cartography Project is a research, editorial, and publishing venture drawing international attention to the history of maps and mapping. The Project's major work is the multi-volume History of Cartography series. Its inter-disciplinary approach brings together scholars in the arts, sciences, and humanities. By considering previously ignored aspects of cartographic history, the Project encourages a broader view of maps that has significantly influenced other fields of study.
Organized by region and time period, The History of Cartography looks at maps in the context of the societies that made and used them. The volumes integrate existing scholarship with new research, examining an unprecedented range of artifacts from local maps to those of the cosmos. The books are extensively illustrated and contain detailed footnotes, appendixes, and reference maps. The award winning series, founded by J. B. Harley and David Woodward, is now edited by a team of scholars and published by the University of Chicago Press.
(hat tip to Karl)