You can certainly cook whole potatoes in the microwave for a fast "baked" potato. The texture won't be quite the same (the skin will be less crisp, and the flesh slightly more dense), but that doesn't stop me from occasionally using this much faster method.
Prick the potatoes in several places (both top and bottom surfaces) with a fork. The fewer potatoes you cook in the microwave at once, the shorter the cooking time. Place up to five or six (depending on the size of your microwave) on paper towels in a spoke pattern and cook for between 6 and 14 minutes, turning them over about halfway through the cooking. The length of time will depend on the number of potatoes you cook at once and the strength of your microwave. For more recipes that you can cook in the microwave oven, see our collection of Microwave Recipes.