About eight years ago I was lucky enough to see organic gardener and author Anne Lovejoy speak at Lewis Ginter Botanical Garden. One of the things that stuck with me was her recommendation to use spent caffeinated coffee grounds to repel/kill slugs and sails. Curious, (verging on skeptical) at first, I've used it for years in thick, perfectly closed rings around my leafy vegetables with great success. The encircled plats stayed intact while those left without the grounds were eaten. Multiply that by seven years, and you have a believer. Apparently the caffeine is a neurotoxin that probably exist in plants in the first place because it protects them from such attacks.
I've seen searching the blogosphere, but in looking for some evidence outside of Ms. Lovejoy's expertise and my own observations, I found two very affirming articles (see below). Perhaps I have such good success because we use a strong, fresh roasted coffee and scoop our beans out into the grinder in what could be called "heaps" for good measure. Regardless, give it a try. What have you got to loose? Coffee grounds add organic matter, small amounts of slowly released nitrogen, and may slowly make your soil slightly more acidic. note... my totally unscientific observations have led me to believe that this really works, unless there is any way for the slug or snail to amble up the leaf without coming in contact with the coffee. Note holes in some leaves above.