Free (or cheap) international phone calls
When 1.5 billion humans are already using WhatsApp, I recognize that this barely counts as a tip. Nevertheless, I’ve interacted with members of the community who still haven’t signed up.
WhatsApp is handy for making free international phone calls.
For cases where the other party doesn’t have a WhatsApp account, it is useful to also have a Skype account, of course.
Beyond WhatsApp and Skype, what tools do you use to make international calls?