There are a number of uses for coffee grinders beyond grinding beans for coffee, and in fact some people keep multiple coffee grinders on hand for different purposes. For cooks who work with a wide array of ingredients and prefer to start from scratch with basic ingredients, a coffee grinder can make a great all purpose grinding tool for the kitchen, and it may be cheaper than products designed for specific tasks such as milling flours or grinding spices.
One of the most common alternate uses of the coffee grinder is in the preparation of spices. Spices tend to taste best when they are stored whole and ground if needed, but this can be a pain every time someone needs some spices. A coffee grinder can quickly grind and blend spices whenever they are needed, along with herbs and other inclusions used for flavor, such as ground dried mushrooms in soup. Using a coffee grinder is less time consuming than a mortar and pestle, and it can yield more even results.
In recipes which call for crushed nuts or bread crumbs, a coffee grinder can be used to create a course crumb, or a more finely milled flour. High quality coffee grinders can even create milled nut flours, which can be very convenient, as such flours tend to be expensive. Ambitious cooks can also grind seeds and grains for various flours, or use a coffee grinder to crack seeds and grains for use as garnishes or textural additions in food.
If a baker needs some powdered sugar in a hurry, a coffee grinder can be used to mill sugar to a finer texture, and coffee grinders can also be used to break chocolate into coarse crumbs for garnishing and baking projects, or to pulp dried fruit for filled desserts. Some people also use coffee grinders for tasks like milling soaked rice for the purpose of making rice noodles, or quickly blending dried and powdered spices while bruising them so that they release more flavor and aroma.
One thing to be careful about when using a coffee grinder for multiple purposes is the transfer of flavors. It is difficult to thoroughly wash a coffee grinder, and some flavors do not mix well. For example, if a coffee grinder is used to grind pungent spices and then coffee, the coffee will taste like those spices. Likewise, a coffee grinder used with nuts will not be safe for use on foods which will be consumed by someone who has nut allergies.