Potato Utilities adds alternatives and additions to Minecraft, all crafted with potatoes and potato derivatives. Currently you can create pleather (substitute for leather in all recipes) and a potato battery (low output power that consumes iron).
To make pleather, you first need plastic. You can create a starchy mixture from 5 potatoes, 3 sugar, and a bucket of water. Smelt it to receive a bucket of liquid plastic, and then pour that on the ground. It will dry into plastic. Pleather can be crafted with 7 plastic (in a "ladder" shape), orange dye on top, and wool on the bottom.
A potato battery can be crafted from 5 potatoes around the bottom of a glass bottle, then iron, plastic, and gold across the top. It will output power until the iron is depleted, at which point it must be refilled (right clicked) with another piece of iron.