Myzerr is a great website to find coupons and deals for a specific topic. You can join groups already set up or create your own for free!
List of some of the groups I like:
Arts n Crafts Supplies Discounts
Las Vegas Coupons & Discounts
(Not Quite) Susie Homemaker
I found Myzerr easy to use and join. Right now I'm just a joiner, but I can see how this would be useful for a business to get the word out and reward it's members by creating a group. Your able to create your own community!
online community platform and see if it's a good fit for you. You can also find Myzerr on Facebook. They have some great articles there on how to promote your business using social media and they have a great deal for group buying promotions!