There are a variety of apps available for the outdoorsy types on iTunes. EveryTrail app is a free one; connect with Wi-Fi and search for trails, select a location and activity and get a list of trails with details of each trail length, elevation change, duration, history, map and directions to the trail head. Then just save the trip and head on out.
A useful tool for campers and boaters is the What Knot To Do in the Greater Outdoors app. It’s sponsored by Columbia Sportswear and users pick a type of rope and the app explains what knot works best. You can save a list of you favorite knots or look through all the knots. The App demonstrates step-by-step instructions with color pictures for guidance.
The most highly rated camping app at the iTunes app store is the Camp & Hike Checklist app. It provides a large variety of checklists for various outdoor excursions. There is also a feature to add and save your own to-do and checklists with a separate Backpacker Checklist App. This app includes where to buy gear and estimates total weights. Also allows users to group items by their functions eliminating unrelated items. Both apps are available for $0.99 each.
As far as map apps go, for $9.99, TopoPointUSA is available and provides high resolution USGS topographical maps. This app does require Wi-Fi or 3G for the app’s GPS and compass to function, but maps can be downloaded to TopoPointUSA Map Case to use offline.