Here comes a list of natural substances and some tips where to use them.

Lemon juice
Scent: lovely, citrus, fresh, clean
Where to find it: lemon tree, supermarket
Active agent: citric acid
Usage:
Has a natural whitening effect, cleans well metals and helps get rid of the lime scale.
Cleans the dirty microwaves

Vinegar
Scent: sorry, it is vinegar. But if used in the required solution, you will not smell anything in a little while.
Where to find it: supermarket
Active agent: acid
Usage:
Deluded with water it is a middle strength acid. It is a disinfectant, can be used to clean windows, glasses, mirrors or to get rid of lime scale.

Baking soda/Bicarbonate of sodium
Scent: none
Where to find it: supermarket, pharmacy
Active agent: natrium-hydrogen-carbonate
Usage:
Great to get rid of nasty smells, soaks up liquids, doesn’t scratch. Keep a little pot of it in the fridge and nothing will smell!

And now, how to get rid of nasty stains?

Coffee stain – delude salt in warm water, soak stained material, scrub it. When stain is gone, wash and rinse the textile thoroughly
Ink – lemon juice, but immediately
Oil, grease – potato starch is the best for that, put a little bit of the powder on the stain, let it stay there for an hour (or 2), brush it and wash it
Chocolate – lemon juice
Red wine – salty water, lemon juice or milk is our help here, soak it for a few hours, scrub it and hope that it goes away

..or try wearing a bib :)