Creating and maintaining relationships with customers can be a challenge. But it’s also essential for a business’ survival and growth. To maintain those relationships, a CRM system is a must. And CRM is one area in which open source shines brightly. Let’s take a quick look at five of the top open source CRM systems. This is by no means a definitive list. Each CRM system covered in this article has been selected based on its rich or unique feature set.