RSS
RSS or "Really Simple Syndication" has been around for a number of years. Unfortunately a lot of businesses online do not use RSS as a promotional tool or any tool for that matter.
To be honest with you, I don't think most businesses know how to use RSS to gain a bigger audience for their products and services. For this reason I have a great book for you below on RSS that will give you a thorough understanding on the subject and how to apply it to your business.