The recommended daily carbohydrate intake is around 300 grams. The actual amount you need will increase if you are larger and more active and decrease if you are smaller or have a more sedentary lifestyle.
Carbohydrate (or "carb") intake has gained a lot of attention in recent years with the popular Atkins diet, which initially restricts daily carb intake to 20 grams. This is often considered to be a bad idea in the long term since it puts the body into a starvation-like state called ketosis. Although there is some disagreement in the medical community, many medical professionals think it is unhealthy to be in a state of ketosis for a prolonged period of time.