Skype for iPhone 2.1 went live yesterday and albeit the update was relatively minor, users running iOIS 4 can now run Skype in the background on the iPhone 4 and iPhone 3GS running iOS4. As a result, Skype users can now receive Skype calls and instant messages while other apps are running or the iPhone is locked. As with the iPhone’s Phone app, you can continue your call while you switch to another application.

Both Skype for iPhone and the update are free.

Skype for iPhone requires iOS 3.0 or later to install and run.