There have been discussions here from time to time about using an electric coffee grinder as a spice grinder, and how to clean it, etc. I'm going to recommend the best grinder out there for this purpose. I'm NOT claiming that this is the best coffee grinder, but I think it's the perfect one to use as a spice grinder.
The things that makes the KitchenAid blade coffee grinder superior as a spice grinder are that the canister that holds the spices/beans is a) large, b) stainless steel, and most important, c) detaches from the grinder so it can be cleaned. The canister is a unit with the blade attached inside, on a plastic base that fits onto the base of the grinder. So no more furious brushing and running rice through the grinder to sort-of remove the cumin scent, etc. You can just take the canister and its top off and wash it thoroughly in soap and water. The motor is strong and easily grinds whole spices finely.