We got a dehydrator this summer, and I found that pears work really well. We have a pear tree that produces barrels of Bartlett pears. I kept them inside for a few days to soften up a bit, but they really were still pretty firm. Used an apple corer to get the center out, then sliced about 3/8 inch thick and soaked them in water with "Fruit-Fresh" for 5 minutes to keep them from browning. Then dried them. They came out really sweet.
I did a bunch of apples the same way, but didn't like them as well as the pears.