Skype updated its iPhone app (version 2.0.1) with compatibility for iOS 4′s multitasking features, including the ability to continue VoIP calls while in other apps. Skype also reverses it’s decision to charge for calls over 3G.
From Skype blog:
In light of that, we no longer have plans to charge a supplement to make calls over 3G. We’re delighted to make it easier for you to talk for even longer and do even more together using Skype.