Apple has released iTunes 7.3 for Mac OS X and Windows, which provides iPhone support, and is required for activation if you’ll be participating in the madness today.

It can be installed via Software Update on Macs, the Apple Software Update control panel under Windows, or you can download it directly from Apple as an installer.

Among the new features are an iPhone tab, which manages backups for multiple iPhones (entire system images, perhaps?), and adds the capability to stream photos from more than one PC or Mac to the AppleTV.