The only one I ever use, and only very occasionally, is "MyTrails".
It's saved me arse a couple times now from getting lost in endless bush for hours. You can set it to use google earth as the map backdrop (make sure you load it while in service - once out of service, you can't display new areas unless previously loaded).
I typically use it on new rivers on the island while exploring. It will track your movements (the gps locator is phenomenal, even when out of service and in canyons or thick bush). It gives you a red dot for where you are. This is especially useful when we are contemplating punching out from the river to the road.
The cool thing is that you can also save your trails, or make/save a way point. You can name the trails or way points (as many points as you want), and you can load data for each trail or way point such as elevation, distance covered, time (start time and total time), etc. Could be useful for when you catch a fish - just throw a pin down and it'll give you the time you hit it at and location.