Have you heard of StoreWoot? If you sell things on Etsy, then you might be interested in this. They use Pinterest to promote items to other Pinterest users. Here's what they say:
"Our network of pinners reaches 11 million Pinterest users. As soon as you promote a product, it will start appearing to these 27,000+ Pinners on our website and we will keep promoting your product to them, till you get minimum 30 repins on Pinterest."
If you use my link below, you get one free credit good toward 1 promotion ($3 value). Doesn't hurt to try it out for free. If it brings extra traffic to your store, then you can buy more credits for a decent price. In the past couple of days, I have gotten 31 repins on the necklace I'm promoting. Not bad for free!