From Jace Cunningham (a facebook friend):
Okay I googled all natural weed killer and came up with this recipe. We bought a little bottle of vinegar, the rest we had, tried it and I could not believe it! Within 3 hours the weeds were dying. It works better than roundup and you don’t drop $20 each time! It will kill grass so use it as you would any weed killer!
One tablespoon salt
One tablespoon dishwashing soap (liquid soap makes the vinegar stick to the leaves)
and up to one gallon vinegar.
Put in spray bottle and spray away, you will be amazed and it’s not full of nasty chemicals!