Calls on Slack - Make voice calls in Slack
toolani - Cheap international calls
Rebel Calling - Internet-free international calling for $1 a month
KeepCalling - Best Rates for International Calls. No Contract, Expiry, or PIN. Use Any Phone, Smartphone or PC.
Skype for Slack - Move your slack discussions to a group skype call
Smart Slack Reminders - Schedule follow-up questions to any message in Slack 💬