Snazzy Maps - Simple & Free To Use Themes for Google Maps
Baidu Map API - Baidu Maps is a desktop and mobile web mapping service, offering satellite imagery, street maps and indoor views
Stamen Maps - Turn any OpenStreetMap location into a watercolor painting
QGIS - QGIS is a desktop geographic information system, or GIS.
MapStyle - MapStyle is a huge library providing a plethora of options for styling the map with detailed customization support.
Google Maps - Find local businesses, view maps and get driving directions in Google Maps.