An repository of publicly available data sets of interest for global modeling/mapping can be obtained directly from http://spatial-analyst.net/worldmaps/.
Check for details, script to download the data etc check this webpage:
“This now contains ca. 100 layers at resolution of 0.05 arcdegrees (5.6 km) and with a complete world coverage. Each layer comes with a raster description file *.rdc, which typically has the same name as the attached layer (description of the fields is available in the README file). The raster description file includes also a link to an R script that (should) show all processing steps from download to export of maps (I advise you to run the scripts step by step because the data sets are usually Huge). If you want to read more about what is all available on this repository (and outside), please read the complete article. You can also browse a gallery of worldmaps from the wikimedia commons. If you think that I have maybe missed some important (publicly available) layers, please let me know. I am sure that there is much more what is available (on and off the web), but I would at least try to be representative.”