Routable Maps for Garmin
From this site you can download for free maps compatible with Garmin software and devices of several countries of the world, that have been generated from OpenStreetMap project data and are distributed under the Creative Commons Attribution-ShareAlike 3.0 license, which lets you copy, distribute and modify the data.
For each area, maps to be installed on a PC or on a Garmin GPS or navigator are supplied, making possible to plan your routes comfortably at your desktop and then use the same maps on your device. All maps are routable, even tracks, and a topographic version (with contour lines) is also supplied. There is also available a version for trucks, which avoid the use of routes not suitable for these vehicles.
OpenStreetMap is a collaborative project which aims to create a map of the Planet with free geographic data and offers it to anyone who want it. Data are submitted by thousands of volunteers who add data (roads, POI's, rivers, etc.) collected with gps receivers from the areas visited or are drawn on aerial imagery. Everyone can participate in OpenStreetMap and add information to the map.
Although more complete each day, OpenStreetMap project is unfinished. So you will probably find areas not mapped or even with errors. The good new is that you can correct this gaps by yourself. If you want to join us, here you have a Beginners' guide. You'll see how easy it is!
In the graphic below you can see the evolution in the number of streets and roads for Iberian Peninsula since maps started to be offered in this web site: