We picked 80 lbs. of apples from our friend's farm a while back, and we're working through on processing them. We canned a good sized batch of applesauce, most of which ended up ruined because our mineral-heavy water resulted in an incomplete seal -- which only became apparent after several days. We have frozen quite a few apple slices, but the best luck (and most fun) has come from dehydrating.
Our dehydrator is a simple heating element with trays that you rotate every 12 hours or so. You could achieve the same results by running your oven on the lowest setting with the door open, although it is energy intensive that way. The cheapest way would be to dry them in the sun, but that requires a little more careful attention.
One key piece of hardware for apples, no matter your preservation method: A peeler/corer/slicer. It takes hours off the process.
