Since coffee is somewhat acidic, I suspect that coffee grounds would make a good mulch around any acid-loving plants, & would be a lot cheaper than those special fertilizers for acid-loving plants.
I have since learned by googling on the web that coffee grounds are a 2-3-6 fertilizer, and that they are quite good for general use around the garden as a light fertilizer. Not bad for lawns, either. Obviously, one wouldn't want to pile them up several inches deep around a plant, since that would be quite a lot of fertilizer at once, but sprinkled around the plants, they are supposed to be good for most of them. They are also reportedly excellent at stopping slugs - - they won't cross the dry coffee grounds, so if that is an issue in your garden, dry some of them out before you sprinkle them around.