Skype

skype

Application homepage: http://www.skype.com
iTunes link: http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware
HTML Link example: <a href="skype:magnatron.nl?chat">Skype us!</a>
Native application URL string example: skype:magnatron.nl?call
Extended example:
Tags:

Please refer to the Skype developer website for a complete overview of all possibilities with this scheme.