Doing it yourself is a great way to insure that you're going as green as possible, since you know exactly what went into the products you're using. A few reliable favorites: Spray surfaces that need cleaning—sinks, tubs and toilets, for example—with diluted vinegar or lemon juice, let it sit for 30 minutes or so, give it a scrub, and your mineral stains will all but disappear.
Getting lime scale or mold on your showerhead? Soak it in white vinegar—hotter is better—for an hour before rinsing it clean.
And to create a great tub scrub, mix baking soda, castile soap (like Dr. Bronner's) and a few drops of your favorite essential oil—careful, a little bit goes a long way here.