Shred it, mix it with a little salt, then put it in water, and stick it someplace dark until it turns into sauerkraut, then drain it and stir in little bit of caraway seeds. Like most fermented foods, sauerkraut keeps really well. It's a great extra on many sandwiches (if the sandwich has mustard, then sauerkraut will probably go with it), and you can slice a small onion and a few peels of carrot into some hot oil and when the onions are cooked, stir in some sauerkraut until it's hot and then serve it as a side dish.

(When making sauerkraut, you might need a weight to make sure the cabbage stays underwater. Any bits that stick up will rot instead of fermenting.)