Twenty-five percent of home water use is consumed flushing toilets. At four to six flushes per person per day, it can add up fast. With my older toilets, at 3.5 gallons per flush, this amounts to about 7600 gallons a year...just for one. My family of four uses around 34,000 gallons a year to flush. That is a lot of water...down the tube, so to speak. My point is, the toilet is a great place to save water and there are some easy ways to make it happen. The most simple and inexpensive option is using displacement...a half gallon milk jug takes up space in the tank and reduces water use. There are also dual flush retrofit kits on the market that allow you to upgrade your toilet with a dual flush mechanism. This video illustrates these two concepts.
Many bathroom fixture companies also sell dual flush toilet models, if you're in the market. And then there is the idea of re-using water to flush toilets. Watch flushing with gray, to see what I'm talking about.