at the moment the creation of OSM based maps for Magellan units is a quite complicated, manual process.
Magellan users will find the maps on the http://www.maps4me.net website for download. We are working on automation and hope to update the maps more frequently.
There is a good soft for creating raster maps from online maps (osm mapnik, bing satellite image an other) for Magellan and some other navi soft.
It is a Mobile Atlas Creator (MOBAC) http://mobac.sourceforge.net/