This nifty app by T-Mobile will turn your iPad into an internet phone for free. All you need is the app and an internet connection through wifi and you can make free calls to your contacts.
RH: Cool app that I use "just because I can." Since I have an iPhone I really have no need for this but it is just cool to call from your iPad. This works a bit like iPad's Face Time accept it is audio only and works across all devices no matter the make.