If you neighbors are a little too friendly, consider adding bushes, trees, or climbing vines to create some privacy. Bamboo is a fast growing plant that makes a great privacy screen, though some varieties of bamboo can be invasive. Evergreen trees are a popular option, because they can grow several feet a year and can be planted close to each other without any problems. If you are looking to fill in the gaps of an existing fence, look into climbing vines. Some vining plants that grow fast are ivy, clematis or hops.