I would like to think yes. Skype is my service of choice, I use it as my primary communications tool right now. Whenever I was deployed to Japan, I used my iPhone and iPod touch connected to the lobby's wifi to make skype calls to my wife's computer. I talked to her every day and never paid a penny.
But here's the problem, Verizon has an exclusive deal with skype for their phones, and I've never used the skype lite program that's available for Android(the evo will be my first android phone). So while it'll be possible, I don't know if contracts will get in the way if it happening.