Skype has just released an update for it's iPhone app and it now supports multitasking! We saw this app demoed at the iOS4 announcement in April, but this is this the first time it has been released to the masses.
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.
No video calling in this update. Maybe next time...
Skype (iTunes Link)