Safari – when viewing a Web site with multiple columns of text, double taping on one will zoom in so it is larger and just that column shows on the screen.
Keyboard Caps – the ‘shift’ key that normally capitalizes the next letter can be locked on by double tapping it. The key will turn blue so you know it’s locked on caps.
Zoom ‘out’ – after you double tap to zoom in on a Web site or a email, double tapping again returns the screen/text to the original view.
Video wide to full – double tapping the screen while a video is playing will change the aspect ratio. Normally videos play in wide screen that may have a black bar along the top and bottom. Changing the aspect ratio fills the screen but also cuts off the edges so you may loose a little bit of the action on the right/left sides of the video screen.