The iPhone 4 / iPad 2 have enhanced camera functionality (FYI: the predecessor models had only one camera, while the new devices now actually have two: forward facing and rear facing).  The new cameras also have functionalities the old one did not, like:

Camera Flash
Open the Camera app; there’s a flash icon at the top left of the screen (looks like a lightning bolt).

Sometimes our iPad 2 or iPhone 4 has 10 or more apps suspended but still running, draining battery life.  To close the apps, double click on the home button until the Shortcut Menu appears.  Now tap and hold on any shortcut icon until they begin to wiggle.  You’ll notice a red bar appear at the top left of each app that’s running.  Click on that bar to close the app.  It will shut it down and unpin it from the Shortcut Menu.

Our friends at Apple have considered everything; even a cleverly hidden way for you to Orientation Lock your iPad 2 / iPhone 4 screen.

When lying in bed with your iPad or iPhone, as you move around, the screen tends to move around with you. While the feature can be really functional at time, at other times it can be really inconvenient (like when you’re trying to read from your Borders eBook, for example).