Try using lemon juice (an acid) to help with grass stains (alkaline). White vinegar can also be used to combat grass stains.
Borax (alkaline) is a great cleaner for protein and acid stains. Corn starch, diluted or sprayed on clothes, is very absorbent and works beautifully on protein stains.
Ditch the petroleum-based detergents and opt for vegetable-based soaps which are better for the environment. Castile soap, which contains olive oil, is a great vegetable-based soap. Use Castile soap or Washing soda on grease stains.
The water and bubbles in club soda work wonders in lifting acidic stains like berries and wine.
Cream of Tartar is color-safe and can be used on coffee or tea stains.
Borax, Washing soda, and white vinegar can be used on stains like tomato juice.