Here's what we're doing with the peels from some of the citrus fruit we bought in bulk. This is a recipe I first used as a child myself. It's a double recipe to start with and we doubled it again this year. It's a very simple recipe. The results are delicious, though with a characteristic slight bitter bite of an aftertaste that leaves you reaching for another delicious sweet piece of peel to quell it.
Candied Fruit Peel
Peels from 8 oranges and 8 grapefruit, quartered
water to cover
4 cups of sugar
yet more sugar
a large heavy-bottomed non-reactive saucepan
Place the peels in the saucepan and cover with water. Bring to a boil and simmer 30-45 minutes, until tender. Pour off water, reserving 4 cups of it. With a spoon, remove the soft inner white part of the rind. You don't have to be obsessive about this, though you'll find less bitterness in the final product the more of the white stuff you get off. Honestly, though, the stuff is darned yummy no matter what you do.
Slice the peel into strips. Set aside.
Place the 4 cups of sugar and 4 cups of reserved cooking water in the saucepan. Heat on medium until the sugar is dissolved. Bring to boil and boil on moderately high heat for about 45 minutes (though this is hugely variable depending on stoves, saucepans and elevation) until a candy thermometer indicates that you've reached the soft ball stage (238 F or 115 C). Add the peel and simmer for 15-30 minutes, until as much of the syrup as possible has been absorbed and the peel has a semi-translucent appearance. Drain in a colander. Then while still warm, toss, a few strips at a time, in a container of a cup or so of additional sugar.
Because we made such a big batch, we had a fair bit of syrup left over and couldn't bear to waste it, so we brought it up to the hard-crack stage and poured it on a cookie sheet, making the largest hard candy we'd ever seen just for fun. We sometimes make little bits of colourful hard candy to use as the windows for gingerbread houses, but I can't image the gingerbread house that would require a window this big!