Google Maps is an excellent tool for active people who like to get around. Navigation provides well-highlighted alternate routes, optional text-list display with voice guidance, street level views with rotation, a peg man to drag around, and easy zoom controls. Users can ask for directions for driving, walking, biking, or riding the bus. Map layers include traffic, transit lines, bicycling routes, Wikipedia articles, attractions, restaurants, and satellite view (toggle for map view). Terrain layer shows contour. The app also provides some icing with latitude and check-in features, screenshots for offline viewing, and extensive web-based help. While we don't recommend that minors broadcast their location, Latitude and check-in allow you to publish your presence at nearby locations even intersections with traveling direction, westbound, for example. (It feels a bit strange at first, like, uh, Can I check out? à la Hotel California.) App mines Google+ info including profile photo and contacts from your device to select groups to "check in" with (the default is public). With Latitude layer selected, you can see all nearby checked-in contacts in maps. Great for family resort vacations or reunions.
Settings has a [Google] Labs list of hopeful yet currently confusing accessibility add-ons including one for blind and low-vision users, one that measures distances and elevation changes, one that makes text larger, and one that displays elevation with directions. Unfortunately, in practice, the usefulness of these add-ons, other than the larger text, is unclear. The few downsides are that it sucks power like most navigation tools, and you must exit the app when you exit navigation.