A good phone is like a good partner. Even though you've spent years together, they're still constantly surprising you with the things they know and do. After a quick fling with a Blackberry and a rebound with a pay-as-you-go phone, we're happy to say we've found a keeper in our iPhone. It's been almost two years together now, and she's still got some new tricks.

It makes calls!
Just kidding. Well, half kidding. The phone is probably the least-used app on our home screen.
But there's a whole other mess of cool productivity tricks that Apple's developers have built into the iPhone. For a roundup of the more common keyboard shortcuts and scrolling tricks, like how to take a picture of the screen or drop a pin in maps, check out Apple's iPhone Tips page.
But the tricks go ever deeper. Here are a few advanced user tips we've found around the web. Did you know your iPhone could...
Turn Itself Off with a Sleep Timer?
Click through the Clock App and into the Timer tab. Set the timer for how long you want your iPhone to stay awake, then select "Sleep iPod" under "When Timer Ends." It'll shut off any open music or video apps, including Pandora.
Make International Calls Easy?
Instead of dialing the country exit code before each international call (That's "011" for everyone in the U.S. and Canada), just dial "+." It'll automatically pop up when you hold down the zero ("0") key. So to call England, you'd dial +44 before the local area code and phone number.
Become a Scientific Calculator?
While inside the Calculator App, tilt your iPhone to landscape mode. You'll be presented with a functional scientific calculator, featuring buttons for squares and square roots; sin, cos and tan; and factorials.
Easily Zoom Out on Maps?
You know you can use one finger to double-tap and zoom in on a map in the Maps App. But if you need to zoom back out, you can do it easily by tapping the screen with two fingers at once. It's way easier than the pinch zoom method if you're holding the phone in one hand or reaching across the car dashboard.
Set Custom Volume Profiles?
If you're sharing your iPhone with, say, a teenaged fan of loud music, you can set custom volume profiles by switching out headphones. The headphone jack on your iPhone registers each individual set of headphones you plug in. The volume you set for each set of headphones will stay consistent each time you plug them in.
(Images: Flickr member Jorge Quinteros licensed for use under Creative Commons, Flickr member Florin Hatmanu licensed for use under Creative Commons)

Shaw's Original Fir...
Neat!
That headphone thing actually explains a lot for me -- it sometimes incorrectly interprets the volume level I was going for between work headphones, normal headphones, and car stereo cable. But knowing what it's "thinking" will help me thwart the attempts at helpful behavior. Thanks!
"It makes calls!" reminds me of that Futurama episode where everyone got eyePhones.
Fry: "You mean eyePhones are phones too!?"
I didn't know the two finger tap. Or the headphone thing. Neat.
VOICE ACCESS If you press and hold the home button while the phone is locked, you can still access Voice Control to place a phone call (or FaceTime call) or get to any of the iPhone’s other voice commands. Voice control can dial phone numbers (“dial 212-555-5555”) or people (“Dial Mom, mobile”), and it can control music (“Play music,” “Play artist Earth, Wind & Fire,” Play album “That’s the Way of the World,” “Play more songs like this,” “Shuffle,” etc).
But did you know that it can also tell you what time it is? Say “What time is it?” and your phone will say the time back to you.
I just discovered the scientific calculator thing myself... would have saved carrying a seperate calculator to my chemistry courses!
Is how to force-quit an app common knowledge?
I didn't know about the headphone thing or the double-tap either. Good to know.
And wait...it's a phone?
@ladykatey i find that quickly double tapping the home button (which pops up with recently used apps) and then holding down your finger over them (as if you were going to be moving them around) enables you to "clear your app history" if you will. it's quite helpful if an app is giving you a bit of trouble like freezing and whatnot. and sometimes apps continue to run and drain battery life unless you completely clear them out with this method. just give it a try! my husband works for apple and when he told me this, it changed my life =)
double-tapping the home button will bring you a screen with all OPEN and ACTIVE APPS at the bottom. Hold your finger over one to get them all 'jiggling' - with a little minus sign in the upper left - and tap on the minus sign to QUIT that app.
Good way to go quickly between open apps, good way to monitor your battery use. GREAT FEATURE.
Double tapping the home button not only brings up the recent used apps menu, it's also scrollable. Dragging left shows more apps. Dragging right shows you a quick audio controller for the iPod app.