Google+ has been the only social networking site that's really helped my website grow in traffic. I've added as many people as I can find in my niche by looking throughout google plus communities that are related or similar to my niche, and I've made a google plus community targeting my niche directly with a link to my website. People searching for keywords related to my niche in google+ find my community and typically add me to their google+ circles when they join the group, which only increases the amount of people that will see my pages rank higher in their personalized google SERPs. I've attempted to grow a following on twitter and facebook with very little results, but google plus has helped significantly with driving traffic to my site. Now all I have to do is post a link to a new article to "public" in google+ and over a thousand people that are targeted traffic for my niche will be exposed to the link. To put it in simple terms: I Highly recommend using google plus for all webmasters.