Skype has updated their iPhone application to run in the background with multitasking in iOS 4.
Call your Skype contacts wherever you may be either on 3G or WiFi. It's completely free to call people on Skype over WiFi, and free on 3G* until the end of 2010.
● Great value international calls and text messages
● Call and text phones anywhere in the world directly from your phonebook, and save with Skype's great rates.
● Instant messages
● With Skype for iPhone, you can instant message one or many people on Skype at the same time, wherever, and whenever the mood strikes.
What's New In This Version:
● Run Skype in the background with multitasking in iOS4. Receive Skype calls and IM while other apps are running or when your iPhone is locked. You can also continue your call while you switch to another application. Multitasking is available only with iPhone 4 and iPhone 3GS.
You can download Skype from the App Store for free.