The part of this story that the Slashdot audience could most easily get in on is aquaponics, which is producing huge yields in some cases and holds a lot of promise for the local food movement.
Aquaponics is a system you can use indoors or outdoors, on large or small scales. It is a closed loop wherein ponds full of fish, usually tilapia, have their water pumped through hydroponic grow beds full of food-growing plants. The all-important third ingredient is a bacteria which converts the ammonia of the fish waste into nitrates which nourish the plants. The water goes back to the fish clean and livable. Once the bacteria are established and in balance to keep this conversion going, the only investment this needs are the energy to keep the pumps going, stable temperatures, and fish food.
Because the density of available nutrients is quite high, the plants can be so too. Their roots mostly just need to grow straight down, so typical planting distances don't apply. The fish too get a cleaner environment, and the usual equations for how many fish per gallon of water can be exceeded. A stabilized, intelligently planted aquaponics system can grow a lot of food - this site (http://portablefarms.com/2013/part-one-sizing-your-aquaponics-system/) claims that 25 to 30 square feet of grow bed is enough to completely meet one adult's supply for table vegetables, and given that you keep the water quality high, the tilapia will make for very tasty protein too.
Because the water is in a closed loop system, very little of it is lost, and aquaponics is radically less demanding of water than traditional agriculture. Because you can grow this stuff indoors, chemical pesticides are neither needed nor desirable, for your sake and the fishes'.
Leafy green plants are the easiest to grow in this way, root vegetables some of the hardest. Tweaks on this system do keep expanding the options, however, like microgreens, wherein you harvest plants in the first two weeks after they've sprouted for a nutrient density four to forty times that of typical mature vegetables. So the question is, how could we make this the most easy thing to get started, so that people with little experience and limited time can skip the refrigerator and east straight from their greenhouse?
Done rightly, this system can shake up food supply as surely as 3D printers are going to shake up industry.