Cartography and GIS
Cartography and the related field of GIS are important for doing and presenting many kinds of research, in various field sciences, and also for social, medical, business, and economic research.
Here is a site that offers both free and commercial GIS data:
Geo Community, http://www.geocomm.com/
At the other end of the spectrum, here is the blog of a boutique cartography company. The blog entries are well illustrated and quite educational.
Please recommend further cartography sites and sources!