A month or so ago, Skype has released its Android application for Verizon phones locked to only work over 3G, WiFi being an option though.
Today, Skype has released an update to its Android app which is no longer restricted to Verizon and it is available in the Market. According to the description, calling using mobile data connection in the US is not possible so you’ll have to stick with using WiFi for the time being.
Android Police have already tested the application and concluded that, indeed, calling via mobile data connection was not possible but the application is well built, takes advantage of the inbuild proximity sensor to turn of the screen while in a call but the program is a very intense CPU abuser and some calls ended due to heavy processor overload.
(Via: Android Police and tip from Telefonica)