marigolds and peas

http://en.wikipedia.org/wiki/List_of_companion_plants

Marigold, Asteraceae

Helps
Calendula Tagetes most plants, especially tomatoes and peppers, cucurbits (cucumbers, gourds, squash), brassicas (broccoli, kale, cabbage)

Deters
nematodes, beet leaf hoppers, other pests

General
Marigolds are a wonder-drug of the companion plant world, invoking the saying "plant them everywhere in your garden". French marigolds produce a pesticidal chemical from their roots, so strong it lasts years after they are gone. Mexican marigolds do the same, but are so strong they will inhibit the growth of some more tender herbs. Certain Varieties of marigolds (Tagetes) can help manage eelworms (Root-knot nematode) when planted the year before[1].
Tagetes has also been found effective against perennial weeds such as Ranunculus ficaria (Celandine), Aegopodium podagraria (Ground elder), Glechoma hederacea (Ground ivy), Agropyron repens (Couch grass), Convolvulus arvensis (Field bindweed), Equisetum arvense (Field/Common Horsetail) and other 'starchy' weeds.

(wikipedia)