Of course, many of you will opt to keep your current iPhone. In that case, here's a list of fun and useful things you can do with the "old" iPhone you once loved so dearly.
Continue to use it as a phone
There are a few ways to use your old iPhone as a phone once it's off a formal plan. For one, you can install Skype (or one of the many VoIP apps) for Wi-Fi based voice over IP calls. There are a few caveats to keep in mind with Skype, however. In order for the iPhone to maintain a Wi-Fi connection, the iPhone can't go to sleep, so keep it connected to a power source. Also, a call coming in via Skype won't ring, only vibrate. So take the case off and put it on a cookie sheet and let it rattle around like a coffee can full of bb's when a call comes in.
Alternatively, if you're the jailbreaking type, get yourself a H2O prepaid SIM card from Best Buy.
Keep reading for more fun ideas.
There are many remote control-type apps available for everything from television and music to computers and cameras. Here are a few options for turing your old iPhone into the ultimate "universal remote."
The Boxee Remote (free) controls the Boxee application. Run it on your laptop or connect a desktop to a TV and you're all set.
Comcast customers can use Comcast mobile App (free), which lets you browse programming options and schedule recordings with your Comcast DVR. Apple TV owners can use Apple's own Remote app (free) to rent and buy movies and TV shows, start and stop playback and a lot more. If you own a Samsung Internet TV, grab their free remote app that gives you control over all of the service's functions.
The granddaddy of them all is POWER A (here's our hands-on review). It's extremely customizable, reliable and learns devices and functions like nobody's business.
Beyond TV, you can control a PC with Remote Desktop ($5.99) or trigger your Canon EOS or Nikon DSLR with DSLR Camera Remote Professional Edition ($19.99).
Now that iBooks 1.1 (free) is available, people can shop in Apple's iBookstore from their iPhones (iOS 3.2 or later is required). It's very nice but not your only option. Zinio (free) delivers any of a huge number of magazines to the iPod.
If comics are your thing, check out Comics (free), Panelfly (free) and Marvel Comics (free). They all offer inexpensive in-app purchases and speedy downloads.
Iceburg Reader does a great job with individual novels, and currently offers popular titles like the Twilight series and The Shack.
And for those of you balking at the idea of doing that much reading on the iPad, I read Stephen King's On Writing with a Palm III e, so I don't want to hear it.
Multi-touch input device
Air Mouse Pro (US$1.99) is a utility that turns your iPhone into a virtual mouse and trackpad. With the companion software running on your Mac, the app lets you do just about everything a mouse or trackpad can do, like select, click, double-click, swipe and so on. It definitely takes some getting used to, but it's fun once you're into it.
Portable gaming platform
This one's kind of obvious, but think about it. Apple is pushing the idea of the iPod and iPhone as a gaming device, and developers are responding. Big names like Capcom and Namco and bringing some of their marquee and vintage titles to the iPhone, and releases from smaller firms like Plants Vs. Zombies and Flight Control have become runaway hits.
The iPhone is smaller and lighter than a PSP or many other similar devices and the games are, on average, a heck of a lot cheaper.
If you've got a 3G or 3GS, you've got a GPS receiver (the 3GS even adds a compass). There are a slew of GPS-based navigation apps available, but I just use the Maps app to be honest. It's always gotten me where I want to go.
Flight Track ($4.99) and Flight Update Pro ($9.99) both do a stellar job of keeping your flight information at-the-ready, and PicPosterous (free) will let you easily share your photos.
There you have several options for your "old" iPhone. It's great to get a few bucks to finance a new one, and just as fun to keep your current model -- still an excellent little machine -- alive and kicking.