WorldPop : High-resolution, contemporary data on population across Africa, Asia and Central/Southern America. Combines the AfriPop, AmeriPop and AsiaPop projects.
Large Urban Areas 1950-2050 : Historic, current and future estimates of populations in large urban areas of the world.
Global Urban Extent : Maps showing urban extent across the world, at 500m resolution, derived from MODIS images. Requires email to author to download
GeoHive : Population and country statistics. Not provided in GIS data formats, but can easily be converted from CSV