Over the past few months, Skype has been testing click-to-call ads on the Web, partnering with local-business directories who pay for the calls. Tomorrow, Skype is set to announce the official roll-out of its click-to-call advertising service with European Directories , one of the largest local business directory services in Europe. Part of Skype’s latest version for Windows (Skype 4.1) comes with a browser plug-in that lights up phone numbers on Web pages. Users can click on the number