I've had my N810 for a while, but I also was wondering about the navigation. I deleted the onboard maps for the "maps"/wayfinder application a while back. As they were on the built-in 2gb sd card, I was not able to get them back during a re-flash. I have since tried downloading them from within the application, but it always either gives me and error or takes too long and never finishes. As far as gps applications go, there are several options for the N810. There is the ever-popular Maemo Mapper, QtMapper, or Maep. None of them offer routing, and I haven't really tested Maep that much. I believe that Maemo Mapper and QtMapper let you download "map tiles" and download instructions to a route while connected to wifi, but there is no turn by turn navigation.