Tomatoes or parsley planted with asparagus controls asparagus beetles. Catnip near eggplant deters flea beetles. Marigolds planted in vegetable gardens repel many insects. Mint repels mosquitoes, cabbage pests and aphids. Spearmint and buckwheat attract beneficial insects.
Nasturtiums deter whiteflies and squash bugs, and act as a plant trap for aphids.
Rue repels Japanese beetles. Cosmos attract beneficial insects. If you're serious about trying natural pest control methods, I highly recommend a book called Dead Snails Leave No Trails . This little book, written by Loren Nancarrow and Janet Hogan Taylor, is full of information about natural gardening. In the meantime, take a new look at some of the smaller creatures lurking in your garden and think twice before trying to eliminate them.