Below is the recipe, if you can call it that, that I got from this 2007 NYTimes article.
1/3 cup ground coffee (medium-coarse grind is best)
Milk (optional).
1. In a jar, stir together coffee and 1 1/2 cups water. Cover and let rest at room temperature overnight or 12 hours.
2. Strain twice through a coffee filter, a fine-mesh sieve or a sieve lined with cheesecloth. In a tall glass filled with ice, mix equal parts coffee concentrate and water, or to taste. If desired, add milk.
I just used coffee filters for the straining and it came out tasting just like iced coffee in good cafes, bringing out the lighter and sweeter flavors that are completely overpowered if you brew that coffee normally. For a fuller explanation of why, see this NYTimes article.
Next up on the iced coffee agenda: Vietnamese Iced Coffee.