Natural Weed Killer 1 gallon vinegar, 1/2 cup salt, dash of dish washing detergent (makes it stick to the weeds). Mix well, spray on weeds in the morning, rejoice in their death that evening. This works best on a sunny day.
I'm actually using this in my yard right now and it works. A bit slower than Roundup but much better for the environment. Kills weeds in about 48 hours. I don't use Dawn instead we use Seventh Generation dish soap.