I built my Laundry Water Recycler (LWR) over a year ago for a cost of about $60, and since then my household has saved four or five thousands gallons of water. You might be concerned that washing with the rinse water could discolor your clothes, but we have not encountered that problem.
This device is intended to work with older top-loading washing machines, where it saves about 20 gallons per load on average. Newer front loaders already use much less water, and, according to this article, they don't have a distinct rinse cycle anyway. Clearly, front-loading washing machines use less water than even a top-loader with the LWR, and the use less energy too. However, in comparing the two, you also need to factor in the energy it takes to manufacture a new washing machine. If you keep your top-loader for a while, then that manufacturing energy is not consumed yet. Anyway, enough green theory, onto the LWR!
The image below shows the LWR. At the bottom of the image is the top of our washing machine. Just above the left side of the machine is the washer outlet hose, which splits into two branches, each with its own ball valve. In this photo, the left ball valve is open, so the water leaving the washing machine will be pumped into the drain pipe at the top of the photo. The valve on the right leads to the storage tank, a 32 gallon plastic trash can, which is suspended from the ceiling on a hanging platform. An outlet at the bottom of the tank has a hose connected to it and this is used to introduce water into the washing machine at the beginning of a washing cycle.