OpenStreetMap “is a free editable map of the whole world. It is made by people from the entire world. People make the maps using data from a GPS device and pictures from airplaces. Map vector information can be downloaded under the Open Database License, and the map pictures can be downloaded under Creative Commons Share-Alike license.
OpenStreetMap allows you to view, edit and use geographical data in a collaborative way from anywhere on Earth.”
Main website: http://www.openstreetmap.org
What many persons don’t know is that there is a number of possibilities to use OSM data (complete or a subset) offline for free.
The main, relevant, websites are:
The files found here are regularly-updated, complete copies of the OpenStreetMap.org database
“This server has data extracts from the OpenStreetMap project which are normally updated every day. Select your continent and then your country of interest from the list below. (If you have been directed to this page from elsewhere and are not familiar with OpenStreetMap, we highly recommend that you read up on OSM before you use the data.) This download service is offered for free by Geofabrik GmbH.”
If you have an Android device (tablet or mobile phone) you may want to have a look at:
“OsmAnd (OSM Automated Navigation Directions) is a map and navigation application with access to the free, worldwide, and high-quality OpenStreetMap (OSM) data. All map data can be stored on your device’s memory card for offline use. Via your device’s GPS, OsmAnd offers routing, with optical and voice guidance, for car, bike, and pedestrian. All the main functionalities work both online and offline (no internet needed).”
An other great software is MapsMe. It allows you to download maps of entire regions or countries to download on your mobile device for offline use. There is a pro and a (free) lite version of the software available. My recommendation is: try the lite version first (it may be sufficient for you anyway) and than buy the pro one. It is worth the money and unmatched as of the year 2014.
If you take part in the mapping in OSM, it will also help to further enhance the data of these software.