The one month free offer has been introduced in an effort to lift awareness among the thousands of people who every day call relatives or friends overseas.
Open to existing customers of the messaging and voice call service until the end of today, the promotion includes free calling to landlines in 40 countries around the world and mobile calls to seven, including to the US, Canada, and Hong Kong.
The offer requires users to have been signed up for Skype for 29 days beforehand, and requires potential customers to provide payment details in case international calls are performed after the initial month period.
Anyone taking up the offer will have to cancel the subscription within 27 days of the start date, namely by the 12th of December, otherwise a charge of $14 for the Unlimited World subscription will be applied.
Microsoft recently confirmed it was preparing to move users from Windows Live Messenger to Skype, which would allow the company to provide broader device support on all platforms for voice and video calls, as well as instant messaging.