I've used the Toddy Cold brew system... it makes an expresso like blend that lasts me for a week or two. Works great until you lose the cork that holds the coffee for 12-14 hours during the brew.
(duct tape works wonders for everything though, including coffee?)
I've mostly used it for making an americano of sorts, but with the warm weather here, I'm excited to try making some iced coffee with it.