I recommend fair-trade coffee, and that medium-sized and large churches purchase it from Equal Exchange, a workers cooperative. Unitarian Universalists may buy it through their Unitarian Universalist Service Committee Coffee Project. Other religious "gateways" include the Brethren, Catholics, Friends (AFSC), Lutherans, Mennonites, Presbyterians, the United Church of Christ and United Methodists. Good coffee, ethically sourced.
But for very small churches and offices -- or where there aren't many coffee drinkers -- this might not be a practical option: I have a back up plan.
Trader Joe's has a tasty, inexpensive organic and fair-trade certified assortment of coffees. I got a pound can of French roast for $5.99 here in D.C. for my Day Job office, and it seems to be well received. (I like their soy liquid coffee creamer, too, but I avoid their frozen vegetables: too many come from China.)