Plant That Repels Garden Pests

I was browsing your web site in the hopes of finding out the name of a plant which may be planted around the periphery of a garden that repels common garden pests. I have read in the past somewhere that such a plant exists, but I can't remember the name of the plant.

There are several plants that have been recommended for this purpose. Probably the most commonly suggested are the marigolds. They are thought to repel both above ground insects and nematodes in the soil.
Members of the onion family are thought to help repel insects. Chives and garlic are often mentioned.
Books on companion planting can provide more details.