According to a new study by BMJ (formerly British Medical Journal), three to five cups of coffee intake was found to be beneficial, except for pregnant women. They do not suggest that doctors should recommend coffee consumption, however.
The amount is maxxed out at five cups. Any more than that are of no benefit and may even reduce or reverse the benefit. In terms of caffeine that is less than 400mg of caffeine/day. Pregnant women should keep their intake to less than 200mg/day of caffeine.
Some of the health benefits believed to be from coffee include incidence of an mortality from cardiovascular disease, incidence of cancer, fatty liver disease (non-alcoholic), diabetes, and cirrhosis.