From the green bean to the darkest roast, here's a scale of coffee roasting and a guide to those different roasts you see marked on your coffee beans:
Starting from the left, here are the grades of roasted coffee: unroasted (green), light, cinnamon, medium, high, city, full city, French, and Italian. There is actually one step darker - Spanish roast, or carbonized beans. At this point the beans are not drinkable; they are fully blackened and in fact can burst into flames at any moment! All the oil in coffee beans makes them highly flammable.
We found this image through Wikipedia Commons and since we've always wondered which was darker - French or Italian? - we wanted to share the answer.
There are actual photos of the beans themselves in these stages at Sweet Maria's - check out the way they crack and darken through the roasting process.