I just found this in an Arthur Schwartz column on the net:
Cold-Brewed Coffee Extract
Makes about 1 1/2 quarts

1 pound good quality coffee, ground for drip
2 1/2 quarts cool tap water

In a minimum 3-quart pitcher or jar, combine the coffee and water. Let
stand for 12 hours. Strain the coffee through a regular kitchen
strainer into a 2-quart jar or pitcher. After the bulk of the coffee
Place the strainer over a bowl for a few hours to get every last drop.

I find that tastes vary about the strength of coffee. For instance, a
guest the other night who was familiar with coffee extract requested
her iced coffee be made with nothing but the extract, ice, milk and
sugar. I needed a shot of water in mine. For morning coffee, however,
I found that three parts water to one part extract, as the
manufacturer of Suzanne? gadget suggests, was too weak for me. I
preferred two parts.

For Iced Coffee
Stir together equal parts of the coffee extract and cold tap water (or
bottled water). Pour over ice. Add sugar and milk to taste.

For Hot Coffee
Use one part coffee extract to 2 to 3 parts just-boiled water.
I just noticed there is a phrase missing in the middle. Anyway, this
has the missing water too--I guess the grounds soak up a lot.