Here's a double whammy for you. Vietnamese site Tinhte (who have a decent record of leaks) has put out a video of what they claim is a) a white iPhone from Apple which is b) running some "test version" of iOS. As you can see in the video on the next page, multitasking in this mystery version presents you with a page full of screens for running applications. They go all jiggly and present the standard close button when long-pressed, and there's a nifty Search iPhone up top, but seems to be missing from the usual swipe to search function normally used to invoke Spotlight.
Is this real? Well, as Federico Viticci from MacStories points out, the Calculator app uses an old icon, as does the Voice Memo app. But iPhone Dev Team hacker Chronic tweets, there's nothing from Cydia like this. In fact, Chronic states unequivocally that this is, in fact, simply build 8A216 of iOS 4. The Gold Master version of iOS 4 was 8A293. Nothing to get excited about today it seems, although the way multitasking works here is kinda neat. Perhaps it will live again in iOS 5. For now, we're not going to say this is indicative of anything but a white iPhone running an old version of iOS 4.
Update: 9to5 Mac posted another video which supports the notion this iPhone is a prototype with 64 GB of memory. Unfortunately they are enthused over what they perceive as iOS 5 features, including such goodies as Facebook integration... We are siding with Chronic on this one and say this is build 8A216.