The University of Texas has a great online collection - Perry-Castaneda.
http://www.lib.utexas.edu/maps/
The USGS, Census, and CIA maps are part of the public domain and can be downloaded and used in your journals. Some are in PDF which makes copying harder others are in JPEG. I find that the country maps from CIA are good for general maps. The "National Atlas" JPEG files are available for each state.