Tomatoes and marigolds are great garden partners. Marigolds release a natural chemical from their roots that keep pests like beetles and nematodes away from the tomatoes.
Bean plants contain good bacteria that helps fix nitrogen in the soil which is good for beets.
Borage keeps insects and pests away from strawberries and also attracts honeybees.
Garlic and other alliums repel slugs that are attracted to nightshade plants like tomatoes.
Rose enthusiasts often plant geraniums among their rose bushes because Japanese beetles are drawn to geraniums, saving the roses.