One thing not mentioned was that used coffee grounds make excellent mushroom starting and growing medium.
You might assume that all the good stuff is pulled out during brewing, but you'd be wrong. In fact, that byproduct is apparently chock full of antioxidants, so it may actually be healthy to eat coffee grounds.
Researchers publishing in the Journal of Agricultural and Food Chemistry analyzed used coffee grounds and discovered that they are full of antioxidants (“dietary phenolic compounds") which help to protect cardiovascular health. In fact, depending on which method the researchers used to extract the phenols, the grounds sometimes contained even higher levels of phenols than the brewed coffee!
I have eaten brewed coffee grounds and they are not bad...waste not!