Custom Garmin GPS Maps
Garmin's GPS maps are proprietary. They make money selling their maps, and don't want just anyone creating them. A couple of years ago some Polish hackers figured out Garmin's internal map format and wrote some software that allows you to create your own GPS maps. Over the years, a growing number of free Garmin maps have been produced for some fairly remote parts of the world. Check out this database, where people freely contribute maps they've produced. You might find something useful.