Nice tip, Lin. I love to see any kind of encouragement when it comes to composting and/or recycling.
As a tidbit of information, when I was giving a class to some gardeners several years ago I read lots of research on coffee, coffee grounds, usage of, etc. It turns out that the used grounds are considered neutral on the pH scale and don't necessarily contribute to lowering the pH of soils. Apparently the acid is water soluble and when brewed it goes into the coffee itself, leaving the grounds at around 6.4 to 6.9, still in near neutral zone required by most plants.
I thought using the coffee (liquid) itself would help some of my gardenias, with it being more acidic than the spent grounds, but it only helps temporarily, similar to how vinegar would only help lower the pH temporarily.
On a good note, this means you can use the spent grounds to your hearts content knowing you aren't increasing the acid level of your soil but rather feeding some good nitrogen to the soil (or rather feeding the bacteria that turn it into N), increasing earthworm population (and their happiness!), and as mentioned above, composting and recycling. Ta-dahh! :>)
Drink coffee. Have fun.
Looking forward to some more good tips!
Shoe
