Last fall I set up some rain barrels next to the house. We get all of our rain in the winter, so we need a lot of storage to catch a significant amount. It's a bit awkward to use the rain water, since it's one watering container (can) at a time. We used the water over the summer for the garden and for keeping the compost bin moist.
A few weeks ago, Dolly convinced me to try catching the shower warm-up water too as an experiment. The warm-up water goes in a 2-gal bucket then we take a shower, then the bucket gets dumped in the watering can. As expected from reading about it on the web, we collect about one gallon per shower. It's not a lot, but, as she says, it's water we can use versus going down the drain. Last weekend we bought another plastic barrel, so I installed a spigot on it yesterday. It is now a feature on the back porch, with access to the spigot at the edge. We will put a few gallons in it every day, rain or shine, so it will add up.
This is considered a very Earthy-crunchy thing to do. I don't consider us very crunchy, but oh well.