Also Fring Prepare VoIP For The iPhone

Even if in pre-release version, the popular Fring it's ready to land on the iPhone, Fring is a instant messaging software dedicated to mobile phones, smartphones, handheld devices and it support protocols like Skype, MSN Messenger, Google Talk, ICQ, Twitter, Yahoo! and AIM, it allow to make VoIP calls via a SIP provider or using the SkypeOut and SkypeIn service.
Fring works perfectly with WiFi networks (if supported by your device) or by using the Internet connection of your device, the rates for calls over landline phone and cell phones vary depending by your VoIP SIP provider or by SkypeOut fee, if you're using this one.
The download page dedicated to the iPhone show all the necessary instructions to download, install and set up in some easy steps your iPhone with Fring.
However, on the Fring website it's possibile to choose your cellphone brand and model and download the appropriate version.