An article on a fairly obscure tech blog provides details about the iPod that have been suspected for a long time but never confirmed. The iPod is a Macintosh. Apparently, the iPod has always been powered by Apple's OS X operating system (a smaller version, obviously, with fewer features). Over all this time, Apple has declined to provide any technical details of what software powers the iPod.
What this means is interesting. It means that the iPhone is not some entirely new device, but a direct descendant of the very first iPod. It also means that there are 100 million more Macintoshes loose in the world than anyone imagined. Apple has already done what Microsoft has been trying to do for a long time with the WinCE mobile platform; Apple already has a huge installed base of "computers" (i.e. mobile devices) now running music players and phones. Cars can't be far behind.