The guided tours are available in both a 38-minute beginner's guide to the entire phone for customers that are new to iPhone, 12-minute edition that shows just the new features added with iPhone 3G and its iPhone 2.0 software for people that are upgrading from the first generation iPhone to the 3G model.
The most interesting aspect of the guided tour is the App Store demo. Once you choose to download an app, the icon will show up on the Springboard with a progress bar, showing how much of the app is yet to download. If you're stuck without a 3G or WiFi connection, the App Store will also be accessible via iTunes, and applications can be downloaded to the iPhone during a regular sync operation.
You can watch the video here.