Cabbage is very versatile and can be used in a wide variety of cooked dishes or raw salads.  Whole leaves may be used raw, or lightly steamed as wraps for meats or other vegetables.
Substitutes:  red cabbage, napa cabbage, savoy cabbage.

Common Names: bok choy, 白菜, Chinese chard, Chinese white cabbage, Chinese cabbage, Chinese mustard cabbage, pak choy, pak choi, baak choi, white mustard cabbage, white celery mustard, taisai, bai cai.
Bok choy has crunchy stems and crinkled, spinach-like leaves. Usually stir-fried with other ingredients, it can be steamed or sautéed and served as a side dish. Smaller heads of bok choy are known as baby bok choy, and are generally more tender than the larger variety.
Substitutes: Chinese broccoli, yau choy, napa cabbage, broccoli, Swiss chard, celery, collard greens, beet greens.

Common Names: Baguio pechay or pechay wombok (Tagalog), Chinese white cabbage, baechu 배추(Korean), wongbok, nappa, or napa cabbage, hakusai (Japanese: 白菜),  celery cabbage, Chinese celery cabbage, Peking cabbage, Chinese cabbage, petsai, shantung cabbage, Chinese leaf (leaves), michihli.
Baechu is a mild, sweet flavored, variety of Napa cabbage, similar to a cross between cabbage, iceberg lettuce, and celery. It has an oblong head with tightly packed pale green to white, crinkled, crisp leaves.  Baechu is probably best known for it's use in the spicy Korean Kimchi dishes.
Substitutes: bok choy, cabbage, savoy cabbage.

Common Names: Red Cabbage, Purple Cabbage.
Red and green cabbage have the same flavor profile and can be used interchangably based on desired color. Red Cabbage may "bleed" color into any dish it is used in.
Substitutes: green cabbage, napa cabbage, savoy cabbage.

Savoy cabbage is milder than common cabbage and can be used in the same types of dishes.
Substitutes: cabbage , napa cabbage.

A few years ago we started growing our own Napa cabbage. I built several wooden boxes to use as raised garden beds and put in a mix of composted steer manure, clean topsoil, potting mix, spaghnum moss, and used coffee grounds. We get a pretty good crop of napa every year now, and just refresh the soil with kitchen and garden compost. I use a dual barrel composter with pretty good results.
Growing the cabbage is pretty easy, just have to protect early growth from the birds and do a bit of weeding.