Maemo Mapper is a popular 3rd party map application. It will do routing, but you must have an internet connection to download it and save it. So if you know where your going ahead of time, you can save the route and then open it when needed.

What I do is set up the route on my computer in Google maps, make any adjustments I need to, then export the .gpx file and open that file in Maemo Mapper.