Fring (App Store link) is a new app for the iPhone and iPod touch that supports free voice over IP (VoIP) telephony. 
Fring lets you use voice and text communications with a variety of services, including fring, Skype, MSN, Twitter, Google Talk and AIM. On the iPhone and touch, service is available using your WiFi connection. 
fring [...]

Internet telephony service Skype has announced a new version, Skype 4.0 Beta for Windows.
The new version focuses on improving video telephony features and offering better usability.
Here are a couple of videos that explain the Skype 4.0:
Skype 4.0 Beta - Introductory Demoby SkypeConversations
Mike Bartlett introduces Skype, and demos the new Skype 4.0 Beta for Windows.
Skype 4.0 [...]

Skype, makers of free telephony software popular with podcasters for recording phone calls, has released the beta version Skype for Mac 2.0. The new version gives any Mac user with an Internet connection the ability to make free video calls to anyone else on Skype, regardless of whether they use the Windows or Mac platform.
Skype’s [...]