Ben Konrath's routable OSM map of Martinique
This map of Martinique is based on data from the OpenStreetMap Project. These maps are routable and as they are updated weekly quite up to date. The download is a gmapsupp.img which is meant to be loaded directly onto the SD Card of your Garmin GPS device. A Mapsource or Roadtrip installer is not available.
OpenStreetMap works that way, that everybody can upload their GPS tracks from which maps from all over the world are being created. This means that the quality of the map depends on the tracks uploaded by the users (you're welcome to contribute to the project by uploading your tracks as well) and therefore the quality differs greatly from country to country, region to region and city to city. As there are continuously new tracks being contributed the maps are getting better and better every day, so if a map of a region is not as detailed as you had expected either join the community and help by contributing and/or come back in a few weeks or months and you will most likely find a better map with more data and information than there was before.