GPSRouteX is a full-featured, auto-sequencing GPS route navigation application for Mac OS X... and it's only just begun! Originally written to make up for shortcomings in existing Mac GPS software, GPSRouteX already includes comprehensive GPS routing and navigation features.
GPSRouteX is designed to take full advantage of freely available data such as GPX files and Google Earth KML files. It is not moving-map GPS software, and it does not come with any data of its own. However, spend a while looking up freely available GPX data, and then pair it with Google Earth and gps2geX, and you'll have a full 3D "moving map" to complement the routing features of GPSRouteX (or use KisMAC to provide a more conventional 2D moving-map, and scan for wireless networks at the same time!). Turn-by-turn driving directions can be downloaded using Google Earth (save the directions as KML and import them into GPSRouteX)... or you can build your own custom routes quickly and easily (then export them to Google Earth so you can see your route on the "map").