If cost is a concern, the cheapest way by far is to make your own coffee at home before you head out.  A 12-ounce bag of decent ground coffee (Starbucks, Tullys, Peets etc.) can be had for $6-8 at the supermarket and makes 2-3 dozen 16-ounce drinks.  Buy a French press or cone filter and a travel mug and you're all set.  If you currently buy takeout coffee five days a week, you'll save a few hundred dollars over the course of a year by making it at home.