Map with worldwide Global Horizontal Irradiation (GHI), Direct Normal Irradiation (DNI) and PV power potential. The GIS data stems from the Global Solar Atlas (http://globalsolaratlas.info).
Data is available as GEOTIF, AAIGRID or KML/KMZ file for GoogleEarth. The link also provides a poster size (.tif) and midsize map (.png).