Source: http://gizmodo.com/5658175/simple-hack-allows-americans-to-skype-over-3g-on-androids
Android users (except for those on Verizon) were understandably excited to hear that the Skype app was now available—until they discovered that it can only be used over Wi-Fi in the US. Fear not, friends, there's a hack!
A Droid Forums poster released a new version of the app allowing for free Skype-to-Skype calls over 3G, like the rest of the world is allowed. The best news is that you don't even have to root your phone to download it—instead, you just download the Sideload program onto your Windows, Mac or Linux computer, and can load apps thattaway instead. [Droid Forums via Engadget]