Check this article on "Whatsapp Salesforce Integration". You can send and receive messages from Salesforce to Whatsapp using Yowsup library, which is a free open source python library. Hope this gives some direction
I have searched and found a Salesforce WhatsApp group and a Salesforce Facebook group.
I have also found a company SaaSnic Technologies who says if you provide your mobile number then they will join you in his WhatsApp group.
SaaSnic Technologies is a reputed Salesforce Development and Consulting company which offer his services for the different domain. Including Information Technology, Automobile, and Retail, Aeronautical, E-Commerce, Legal Services, Professional, Investment and finance and so on.
The information I have filtered I tell you, If you want to join SaaSnic Technologies then join his Whatsapp group on your own risk