I really liked iTopoMaps on iThings for downloadable maps, but it stopped working with current iOS software and didn't seem to get any updates. Now I'm using MotionX-GPS for that purpose. Just make sure to download any maps you're going to need in advance, preferably over Wifi.

When I'm out and about, I'll drop a "pin" at my campsite, car, trailhead, or any other place that I might want to be able to find again. Then I put the gizmo away (in a water- and shock- resistant case) and navigate with map and compass. For me, it makes a good backup.