Buying locally roasted coffee and grinding it yourself is a key to your best possible coffee, but coffee grinders aren't the easiest to clean. Use dry rice or stale bread to quickly clean out old coffee.
Commenter Jacknut tipped us to this idea, and a lot of how-to and foodie sites back it up. INeedCoffee and eHow agree with Jacknut's basic premise: put in enough dry, uncooked rice to reach the top of the blades, run the grinder for a bit, then check out the rice as you dump it. You should see some of the deeply embedded brown stuff clinging to the rice. Give your grinder a final wipe-down, and maybe wash the lid (separately!) with water, and you're good to go.
If you lack for rice, or want to try another solution for old coffee left in the grinder, Chow suggests dry, stale bread, in a chunk about the size of the leftover grounds — or spices, if you've converted your grinder toward that end — you're trying to get out. Found one of these tips to work better, or have another grinder solution entirely? We await your suggestions with jittery anticipation.
How to Clean a Coffee Grinder [ eHow.com]