A big new feature has been added to the multi-tasking user interface in iPhone OS 4, and that appears to be a widget interface for the iPod app. If you flick to the left of your first window of open apps, you are greeted with a few new buttons.
A stationary iPod button to quickly launch the app, iPod music controls, and Orientation lock. The orientation lock is just like on the iPad, but instead is controlled via this new menu. Tap once to lock in portrait, and again to unlock. The iPod music controls are similar to the ones that used to appear when you double clicked the home button.
This could be the beginning of mini-widgets coming to iPhone OS 4. We'll update if we find anything else.