Sauerkraut is a delicious, inexpensive and delicious way to preserve cabbage.
Sauerkraut is especially rich in vitamin C and probiotic bacteria. It has been traditionally used to provide sufficient vitamins during long winters when fresh fruit is not available. It was used by Captain Cook to successfully prevent scurvy on long sea voyages. In addition to this Sauerkraut is said to have many other beneficial health effects. See this Wikipedia article for details.
Sauerkraut also contains high quantities of Vitamin K, Vitamin B6, Folate, Iron, Potassium, Copper and Manganese.