Skype is the most popular software used to call other PCs using the Voise over IP (VoIP) technology. Use this free tool to check the status of a Skype user. Remember that the user has to be enabled the privacy option "Allow my online status to be shown on the web", else the output will always be "Unknown". The available status messages are: Unknown, Offline, Online, Away, Not Available, Do Not Disturb, Invisible and Skype Me.