Well, you can use it for another batch of cider if you'd like, also you can make bread with it! For cider just pour the juice over the "waste" and let it start to bubble. It should work the same as a yeast starter. And as for bread, just use the "waste" to replace a little water in the recipe, and don't add more yeast to the mixture. It will take quite a bit longer to rise than normal yeast, but it will work all the same.
Simple bread recipe:
3 cups of flour
1 cup of water
.5 cups of "waste" Cider/yeasty goodness
pinch of salt
pinch or two of sugar
mix, let rise till doubled in size, punch down, knead, let rise once more till double it's size, transfer to bake pan and let it rest for an hour or so, then pre-heat the oven to 375'F and then bake until bread sounds hollow, and is crispy golden brown.