I am not a greenie or enviro agitator, but this caught my eye last week. It turns an ordinary toilet into a dual flush toilet, like those costing hundreds of dollars. The article had an eight-year-old install one in a few minutes with no tools. In full disclosure, I have no financial interest in this product.
The dual-flush technology allows lower water volumes for liquids and paper. A second, full-flush uses the standard amount of water for solids. It is estimated that 80 percent of flushes do not need the full amount of water. This thing costs $19.00 on Amazon. It has a piece that replaces the flapper and an extension that replaces the handle.
Read the customer reviews. It is not a panacea, but seems like it is worthwhile to consider saving a few bucks on your water bill. It is called HydroRight. LINK