The non chemical way:
If you want to repel ants, you've got a number of alternatives including vinegar, cayenne pepper, cinnamon, cream of tartar, salt and perfume. Place any of these along their path and keep trying until you find one that works.
You can kill the ants by dehydrating them with instant grits, which you'll find in the cereal section of most grocery stores.
This was taken off the greenscene site.
Heres somemore from the vegsoc:
Ants are harmless and are only looking for sweet stuff when they come into the house, so keep all sugar, jams, honey, cakes etc in tightly closed tins and jars. Wipe kitchen surfaces down with a solution of equal parts of vinegar and water. Find where the ants are entering the house, block up any obvious holes and cracks and sprinkle red chilli pepper and/or paprika and/or dried peppermint or pennyroyal across their line of entry. We have also read that they dislike coffee grounds, if placed in a dish on the worktop, they will avoid the entire worktop. Crumbled bay leaves or sprigs of pennyroyal in cupboards and corners may also act as a deterrent.