I used to use this app a lot once I had my Nokia N95. When I upgraded (was that really an upgrade?? lol:)) to an iPhone I really missed this app. Basically it allows you to to skype calls and chats. Calling works only with WiFi though (on N95 it was working through 3G as well but I suspect that Apple won’t allow this to happen cause of telcos contracts) but anyway it’s still a great application.
You can download it from the App store by searching for “Fring”.