Alongside its refreshed hardware lineup, Amazon (and Microsoft) announced back in September that Skype calling was coming to Alexa devices later in the year. Well, it's later in the year, and the new functionality is rolling out starting today. You can link your Skype account to your Alexa devices in the Alexa app.
To set up Skype calling, fire up the Alexa app on your phone, go to Settings, then Communication, then Skype. You'll sign into your Skype account, and that's that. You can then give your Echo commands to call people on Skype; a device with a screen and a camera will default to a video call, while a regular Echo will make a voice call.
It was already possible to make calls and video calls with Alexa devices, but Skype is a huge, cross-platform service, so being able to make calls with it through Alexa is a big get for Amazon and a potential selling point for Echo devices.