Be sure to read their Privacy Policy beforehand:
http://www.skype.com/company/legal/terms/tos_voip.html
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(May be worrisome for some...)
Article 14 ? EMERGENCY CALLS
14.1No emergency calls. You expressly acknowledge and agree that the VoIP service provided by Skype does not and is not intended to support or carry emergency calls to any type of hospitals, law enforcement agencies, medical care unit or any type of emergency services of any kind and that Skype is not liable in any manner for such calls. In the event that, with Your permission, another user uses Your Account or Skype Group member Account, You are responsible to inform that user that it is not possible to support or carry emergency calls with the Skype VoIP service.