Skype for Slack - Move your slack discussions to a group skype call
Evercontact - Your contacts always up to date and automatically with Evercontact.
Calls on Slack - Make voice calls in Slack
CONTACTBOX - CONTACTBOX combines the simplicity of an address book with effective functions of a CRM system.
Pingly - Your communication hub — Email, text & voice in one app
Pobuca Connect - Connect with your contacts.