MacVideo has a nice feature video in Tearing apart the new iPhone 3GS: Interview with Kyle Wiens from ifixit.com:
"The iPhone 3GS has only just been released and already people are tearing it apart. We caught up with Kyle Wiens, CEO of ifixit.com and documented the opening up the new iPhone and a breakdown component by component to find out exactly what this thing is made of. This provides a rare glimpse into the way Apple manufacture their technology and reveals secrets such as processor speed and other possibilities for those who love to investigate technology."
ifixit.com, a Mac-oriented parts resource with repair guides, has more user-contributed sneak peeks inside the hottest new gadgets on their iPhone and other Gadget Teardowns page.
Not all interesting teardowns have video; see for example Teardown: Inside Cisco's Flip UltraHD digital camcorder.
Apparently teardowns are new class of tech reporting. Similar phone teardown are featured by phoneWreck. Here's another iPhone 3Gs Teardown from Teardown TV, a series just starting from EE Times: