Have you been looking for nighttime satellite imagery that dates back to 1992? Or perhaps you are interested in population growth around the Globe? If so, NOAA has a dataset you need to check out: global mosaics of the DMSP-OLS Nighttime Lights Series. This dataset features 30-arc second pixels and extends back to 1992 spanning six versions of the DMSP satellites. You are able to download the raw data used to create these global mosaics from this website, though admittedly I had a hard time getting access to any data in a useable format. There are also a variety of online maps as well as WMS and WCS portals that give you access to the various products offered from the DMSP satellites.
Until my next edition of Free For All!, happy hunting for free GIS data!
Brock Adam McCarty