Skype 3.0 app for iPhone/iPod Touch lets you make video calls right from your iOS device to another iOS device or computer running Skype application.
Skype blog post says
This season is very special as we are releasing a new version of Skype for iPhone and iPod Touch with video calling.
Skype video calling is supported over WiFi and 3G* data connections. You can enjoy video calls with users on all Skype desktop versions and with other Skype for iPhone, iPod Touch, and iPad users.
You can make video calls in both portrait and landscape mode and use both front and back cameras.
Users on iPhone 4, 3GS and iPod Touch (4th Generation) can enjoy full 2-way video calling. Users with iPod Touch (3rd Generation) and iPads can receive video.
Download the app straight from AppStore