Skype for Slack - Move your slack discussions to a group skype call
Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Aircall Now - Make voice calls inside Intercom Messenger 📞💬
Harvest - Simple time tracking, fast online invoicing, and powerful reporting software. Simplify employee timesheets and billing. Get started for free.
Calls on Slack - Make voice calls in Slack
RescueTime - Time management software that shows you how you spend your time & provides tools to help you be more productive.