Cleaning burr coffee grinder
I use Minute-Rice to clean mine (any instant-rice will do - it's partially cooked, so it's softer than raw rice and does a better job cleaning).  I just run a bunch of rice through until it's coming out clean, then run some old beans through before using it for coffee.

Here's a Youtube video on it.  I'm sure there are tons more.  Check out the CoffeeGeek or Home-Barista forums for more information than you ever wanted.