Garmin Offers Process to Put Your Maps on its Devices

Essentially Custom Maps allows you to upload georeferenced JPGs onto your device. Per the press release:

The first step to creating Custom Maps is to save your existing map in JPG format, either by scanning a paper map or converting a digital file. The second step is to georeference your new map image, which can be done easily by using Google Earth to line up key landmarks with those depicted on the map. The final step is to save your Custom Maps to your Garmin device and you’re ready to go explore. To see these steps in further detail, to find and share maps with other users and to join discussions about Garmin Custom Maps, visit http://www.garmin.com/CustomMaps. Custom Maps should only be created from maps that are in the public domain, for which you hold the copyright, or that you have permission to use from the copyright holder. The original map’s accuracy in scale and illustration is also an important factor in creating quality Custom Maps.