not anything through verizon. You can use sipdroid and gvoice callback in the market for wifi calling with no extra charge though.
Indeed, Verizon has always been a little 'feature restrictive', to put it lightly (this is the company that wouldn't even allow you to use bluetooth transfers or your own music as ringtones for years), so I doubt they'll allow a joint version of Skype or anything like that to support it any time soon, but, as PJNC said, there are third party apps that support it. Keep in mind, though, that Google Voice (gvoice, as PJNC called it) will only have free calling through the end of the year, and will begin charghing (it is being reported) low rates to make calls through it next year.
There's LOTS of third-party wifi calling options. Google Voice, Fring, Skype are the three that come to mind, but I know there's plenty of others too.
I used Fring for my girlfriend for a while because where she lived AT&T was the only carrier that had any reception, her parents had T-Mobile and I have Sprint, so instead of her having her own individual AT&T plan with a crappy phone, we saved her money by putting her on my plan with a smartphone and doing Fring wifi calls (great high-speed internet, but no cell reception, it's a heavily wooded area near a college >_>)... Worked great for the 4 months we used it.
I love Verizon, I have a samsung Galaxy S 3GS which I love. BUT, I hate the fact that when I am overseas I cannot use Skype WIFI while I can use WIFI on my phone for everything else....I cannot afford to use Verizon (no one can) international calling from overseas to stay in contact with my family. 1) What is the reason why Verizon prohibit use of Skype WIFI? 2) is there plan to change that in the near future? 3) What about going to 4G /LTE is there a plan to add SYPE WIFI for international calling from outside USA? 4) Is there any Verizon phone that allows use of Skype WIFI ? I hate to think that I have to go to AT&T ....
Can someone shed some light?