You can put a mechanical timer on almost anything you don't want running all the time.
I have a large (210 gallons) aquarium. I have it on a timer so that it only runs the lights, pumps, etc. in the evening when it's nice to look at the fish. (Don't worry, they are all carp family..)
My parents have a small pond with little waterfalls which is very nice to look at, but doesn't need that pump running 24-7 either. I set that up on a timer and it saves a HUGE amount of energy.
I also have an exhaust vent above my stove. The flap works pretty well to keep the wind out, but it is all just plain sheet metal and radiates winter cold into my house. I covered it with radiant barrier, and that made a huge difference.
I also set up a system that reuses laundry water to flush my toilet. I live where winters are fairly cold, so a gray water system for water plants outdoors would NOT work year-round. On my gray water system, everything is kept indoors until the backwater system, which is all buried (freeze-proof) pipe.
Filter your Laundry Graywater with Marsh Plants!
I also helped set up a rainwater collection at my parent's house. It's used for watering the garden and fruit trees, saving electricity and wear and tear on the well pump.
Rainwater Collection gets bigger, Part 2