SugarCRM is a commercial open source product that is available as a software as a service cloud offering. Specifically it deals with managing sales, service, contracts and projects for all sized companies.
Their latest release (6.x) has gone a long way to help consumers of CRM systems. In other words, once up and running it is easy for any sales representative to use.
In addition, it has inbuilt activity streams, LinkedIn and Twitter integration and, "out-of-the-box", it comes integrated with InsideView; a powerful sales intelligence product.
As soon as a lead or account is entered; SugarCRM automatically finds and connects the information from social media sites. This is very useful for any sales department.
Combining this with InsideView gives you everything you need to know about a lead or prospect in one easy to use interface. More popular CRM products, in our opinion, tend to be hard to use, overly complex and come with clunky social media integration.