If you use the iPhone's headphones (or a third-party set with click-control), iPhone 2.1 adds one more feature to the clicker: triple-click to jump back one song. So one click will pause the current song, two clicks will jump forward one track, and three (very quick) clicks will jump backward one song.

To enter a period while using the on-screen keyboard, hold down the Punctuation key and slide your finger over to the Period button. Then release it. (This works for all punctuation)

Ever scroll pretty far down a Web page, only to find that the address bar has disappeared? No need to scroll back up.instead, tap the top part of the screen. The address bar will reappear, regardless of where you are on the actual Web page.

Before you begin browsing, rotate the phone horizontally. Now tap the address bar.

When keying in Web addresses, the iPhone gives you a very useful .com button that lets you add the four characters in one press. But as with the desktop version of Safari, you can even leave that out: Safari will automatically add it for you. Bonus tip: hold down the .com button; you'll be presented with a list of alternate domain endings, such as .net, .edu, and .org.

Use two fingers to scroll within a frame on a webpage. Use one finger to scroll the entire webpage.

By swiping an email from left to right you will quickly delete that email message.

If you don't use Google Maps:
Settings > General > Location Services

On a typical website, double-tap a column of text to zoom right into it . the iPhone will zoom the view to fit the width of the screen. Double-tap the screen again to zoom back out.

Double-tapping a picture will automatically focus in to show a close-up. Again, this auto-zoom will fit the width of the iPhone's screen.

Use double-tap to zoom in/out on photos in the iPhone's Photo app and toggle between full screen and letterbox mode during video playback.

A double-tap is an easy way to incrementally zoom into a section of a Google Map.

Tapping two fingers on the screen (ie. first and index finger) will zoom back out the same way.

Instead of pinching out to zoom out, if you tap the screen with two fingers, the page will zoom out.

Single tap the time at the top and you'll jump back to the top of the page.

Double tap quickly just above the .+. icon and this will bring you down a page.

Instead of pressing the 'shift' or '.?123' buttons and letting go to capitalize a letter or get a number, here's a cool short cut. Tap the 'shift' / '.?123' button and hold your finger down, then slide to the appropriate letter or number and let go.

In order to save images from Safari / Mail, just click and hold down on the photo until you see Save Image, Open Link or Cancel. Click on Save Image.