Crushed egg shells and DE also work to help with the slugs. A ring of copper around plants that get badly effected by slugs works great at keeping them away. The copper shocks the slugs and they die. Only problem with that is buying copper is expensive. I did see a few years ago a farmer who took his pennies and glued them together to make collars for his plants. He claimed it worked like a charm and was well worth the expense of not carting off thousands of pennies to the bank to cash in.
The starbucks by me doesn't always have coffee grinds, A few other people in my area also pick up the coffee grinds. I have seen them advertise they do give out coffee grinds on request. I've only gotten grinds from them once. During September to June I get my grinds from the school coffee shop.