Sauerkraut! The best use of cabbage in my opinion. Fermentation in general is one of those processes that can be applied to so much! And if done in the right way, is super healthy!
Chop the cabbage in to thin strips, add 10 grams of salt per pound of cabbage and work it with your hands so the fibers are broken up. I like to throw some caraway seeds and some mustard seeds in before putting it in the cupboard for a week. I also check on it daily to make sure all the cabbage is submerged.