Peas, corn and squash are known as the "three sisters" when planted together. All of these vegetables are beneficial each other in some way or another. Corn acts as a support for pea vines that grow tall. The peas then return much needed nitrogen to the soil that is necessary for growing productive corn. Corn is delicious to both humans and animals. Protect your corn by planting squash around it in a circle. Squash vines are naturally prickly. These pokey spines deter squirrels and other animals from getting to the corn, climbing up the stalk and ripping off the ears.
Basil is a good companion plant for both tomatoes and peppers. Some gardeners think that growing these plants together improve the taste of the peppers and tomatoes. Basil also keeps some pesky insects from eating the fruit and the leaves of the plants. The benefit that the basil receives if that the taller tomato and pepper plants provide shade for the basil during the hottest parts of the day.
Beans and carrots work well together in that carrots absorb the nitrogen that is in the beans. Also carrots are cooler weather vegetables and mature sooner than the beans. Plant the carrots at the appropriate time for your gardening zone. Plant the beans at the appropriate time for your zone right along side the carrots. As the carrots mature, harvest them as they are ready. This also helps you save space in your garden if you do not have a lot of space to work with. Beans also grow well with other root crops such as beets and radishes, which also mature earlier in the season.
Broccoli has several companion plants. Many herbs, such as rosemary, dill and sage keep insects away from the broccoli. Plant bush beans, celery, onions, tomatoes or cucumbers among the broccoli plants. This is a space-saving idea as well as beneficial to the vegetables. These vegetables have improved flavor when planted near each other.