Coffee grounds are great for your compost, it adds lots of nitrogen.
On a side note I can also add that coffee is GREAT to combat snails in your garden, they die very quickly if they come into contact with it. It works like a neurotoxin on the little bastards. I basically saved my harvest of corn, squash, beans and cucumber using the cheapest coffee I could get last summer
The coming summer I have plans to construct coffee traps that keeps the rain from washing away the coffee and keeps the snails at bay. I don't drink the shit but it's a truly awesome weapon against snails