I've been freezing leftover coffee and using it to make afternoon milk and cookies that much more delicious (and caffeinated). This afternoon I'm going to put my caffeinated ice cubes in the blender with some soy milk and agave nectar to make a coffee slushie.
Update: 4 coffee cubes + 1 cup soy milk + a quick swirl of agave nectar blends into a nice coffee slushie, but my favorite use of the cubes has been iced coffee to go - coffee cubes, soy milk, (unbleached) sugar in a (clean, repurposed) jam jar, stuck in my bag to take to the park with the boys. An hour later, when the cubes and the sugar are fairly melty, and I give it some vigorous shaking, and open up my frothy, sweet, cold coffee drink, I am so much more cheerful about pushing Felix on the swing or helping Desmond make decorations (again) for Rocketjohn's (new imaginary friend) birthday party (again).