My wife loves her some cold brewed coffee. She takes coffee grounds, dumps them directly into a gallon of cold water, and leaves it in the fridge overnight, or sometimes for a day and a night.
In the morning, she strains it through a filter leaving a gallon of very concentrated black coffee - which is amazingly smooth and not bitter at all. She likes "strong" coffee by most people's standards, so she mixes it 2:1 with water.
The gallon stays in our fridge. At her 2:1 ratio it's good for about 100 cups of coffee, and that lasts her a good two weeks or so.