iPhone 3G can make calls through Skype.

iPhone 3G owners can make cheap international calls through the Skype app. This app can be downloaded from the iTunes through the iPhone 3G. This app will allow the user to make free contacts with friends who are online if they are too using this Skype app.

According to the Skype following are possible.

Free Skype-to-Skype calls from any Wi-Fi zone to other Skype users worldwide
Call landline or mobile phones at Skype's great low rates from any Wi-Fi zone
Send/receive instant messages to/from individuals or groups via 3G, Wi-Fi, GPRS or EDGE (whichever is available)
Receive calls to a personal online number on Skype
See when Skype contacts are online/available to IM or talk

Skype for iPhone requires a Wi-Fi connection to make free Skype-to-Skype calls or low-cost Skype calls to mobiles and landlines. Users will not be charged by Skype for making and receiving Skype-to-Skype calls using an iPhone or iPod touch. Skype's normal low rates apply if using Skype to call landlines or mobiles.
Already millions of iPhone users have downloaded this app from the Apple's iTunes store in the internet.

Skype for iPhone Get it Now: Click here