Apple has released the third beta of iPhone OS 4 and Xcode SDK. iPhone OS 4 beta 3 is available for the iPhone 3GS, iPhone 3G, 3rd and 2nd generation iPod touch.
To download you need to be a member of the iPhone Developer Program.
According to Mac Rumors this version of the beta include an iPod music control interface in the App switcher and the ability to lock the orientation of the screen:
Arabic version of this post on SaudiMac.net.