Recs.
Updated
OsmAnd Maps & Navigation is a free map and navigation application that utilizes OpenStreetMap data.
SpecsUpdate
Pros
Pro Based around crowdsourced OpenStreetMap data
OSM provides a map editable by everyone; just like the web-based encyclopedia, Wikipedia.
Using a community edited map allows one to correct isses they encounter. Combined with the monthly turn around, these edits are added for navigation quickly.
Pro Profiles for driving, cycling, hiking, walking, trucking, motorcyclists, public transport users and so on
Comes with many different profiles that highlight different features of the map, and changes the behavior of the interface to make it useful for each activity. You can edit to the profiles to make them fit your use case better, and even create custom profiles which highlight different features on the map.
Pro Excellent general map viewing
Sometimes one needs more than just navigation, they have a need to view a map or specify a specific route. OsmAnd provides a very nice, detailed map. This can be good for seeing what is around you or showing a place you are talking about to a friend.
It also provides a means to add waypoints on the map which can be used to dictate a specific route (not simple enough to do routinely).