"This program is intended to make working with the Generic Mapping Tools (GMT) easier. iGMT provides a graphical user interface for GMT and is written in the Tcl/Tk computer language. Besides supplying a user friendly way of handling GMT, iGMT comes with built-in support for many different geoscientific data sets, such as topography, gravity, seafloor age, hypocenter catalogs, plate boundary files, hotspot lists, CMT solutions etc."
An interactive mapping tool with a built in datasets.
"A collection of 6,638 worldwide and regional geographic data layers, scanned historic maps and associated descriptive information that can be searched mapped and downloaded for use for use with your GIS software."
After you get past the ESRI restricted data, there is some fun stuff...