Maps

Blue Marble Next Generation (500 m / pixel)
NASA Goddard Space Flight Center Earth Observatory http://earthobservatory.nasa.gov/Newsroom/BlueMarble/

Earth's City Lights
Data courtesy Marc Imhoff of NASA GSFC and Christopher Elvidge of NOAA NGDC. Image by Craig Mayhew and Robert Simmon, NASA GSFC.

Shuttle Radar Topography Mission (SRTM30, 1 km / pixel )
NASA Jet Propulsion Laboratory http://www2.jpl.nasa.gov/srtm/

Micro World Data Bank in Polygons ("MWDB-POLY / MWDBII")
CIA ; Global Associates, Ltd.; Fred Pospeschil and Antonio Rivera

Temperature and Precipitation Maps (July and December)
A combination of two datasets:

Street Map

OpenStreetMap
The street maps used in Marble via download are provided by the OpenStreetMap Project ("OSM"). OSM is an open community which creates free editable maps.
License: OpenStreetMap data can be used freely under the terms of the Creative Commons Attribution-ShareAlike 2.0 license.

OpenStreetMap
The routes used in Marble via download are provided by the OpenRouteService Project ("ORS").
License: OpenRouteService data can be used freely under the terms of the Creative Commons Attribution-ShareAlike 2.0 license.

Cities and Locations

World Gazetteer
Stefan Helders http://www.world-gazetteer.com

Geonames.org
http://www.geonames.org/ License: Geonames.org data can be used freely under the terms of the Creative Commons Attribution 3.0 license.

Czech Statistical Office
Public database http://www.czso.cz

Flags

Flags of the World
The flags were taken from Wikipedia (http://www.wikipedia.org) which in turn took a subset from http://www.openclipart.org and reworked them. All flags are under the public domain (see comments inside the svg files).

Stars

The Bright Star Catalogue
5th Revised Ed. (Preliminary Version) Hoffleit D., Warren Jr W.H., Astronomical Data Center, NSSDC/ADC (1991) http://adc.gsfc.nasa.gov