NetHunt CRM is service to turn your Gmail inbox into a full-featured CRM system.
It helps you organize your business processes into the easy-to-manage and analyze Records available from Gmail. This allows you to manage and supervise sales, clients, project, support cases and other business activities within the familiar Google Apps ecosystem.
If Google Apps / GMail is enough for you, this is a great extension, adding CRM elements to the tools you're already using on a daily basis.
Pros:Innovative and approach towards CRM, simple in its nature and idea, cold mailing features
Cons:CRM based on Google Apps has its limitations.