One of the most common side dishes in Korea is Kimchi.
I don’t make Kimchi at present, because our household doesn’t consume enough to make it worth while.
This is what I buy at the supermarket usually (3,700 won for 500g, US $3.90). This one lasts me about 2 months. You can make soup, fried rice, etc with Kimchi.
You can learn more about Kimchi from wikipedia