Videochat apps

FaceTime, the built in App for iPhone now simply works over your cell network. So you no more need Wi-Fi to make video calls. This is bad news for apps like Tango that did  the same purpose in the past.

Adium

Mountain Lion comes with a new instant message app called Messages. It will let you use all of your IM services like AIM, Google Talk and Jabber at once. It also lets you send iMessages to iOS devices. Adium, the instant messaging client for Mac OS X is out now.