Magellan (of all names) has a solid overview of navigation software options for Windows Mobile over at Brighthand. Apparently, when not sailing around the world Magellan is testing iGo, Mapopolis and TomTom Navigator software. Who knew?
This review was well worth reading because I liked the approach that Magellan took; the review pits all three applications against each other in five everyday navigation scenarios. All of the apps did a good job overall, but only one was the "strait" up winner. I don’t want to ruin the voyage for you, so you’ll have to hit Brighthand for the details. Bon voyage!