Here's a secret they didn't tell you when you bought a 3G iPhone: One of its best features—the ability to run new applications found on iTunes—is also possible on the old iPhone with an easy software upgrade. Plus, you can hack your first-gen to run unofficial apps alongside the sanctioned ones (known as "jailbreaking" the phone). And remember that your deactivated iPhone still has built-in Wi-Fi and Bluetooth as well. With all this at your disposal, there are lots of ways to give a first-gen a second life.
Apple's free Remote application is the slickest way to control your AppleTV or Mac's iTunes with an iPhone, but there are other free apps for controlling your TiVo (code.google.com/p/tivoremote), your MythTV home-theater PC (trac2.assembla.com/mymote/wiki) or any computer (code.google.com/p/telekinesis).
Turn the page to see how to turn it into a GPS device.
xGPS ($75; xgps.xwaves.net) uses a small GPS receiver that plugs into your phone, along with software to give you turn-by-turn directions (you must have a jailbroken phone to use xGPS). Coming in January, LocoGPS (gomite.com) will do the same thing with a GPS receiver that connects to your iPhone over Wi-Fi.
Turn the page to see how to turn it into a VoIP phone.
Although your cell number is now on the 3G, your old phone can still make calls over the Internet using Wi-Fi. Truphone is found in the app store; calls cost between 6 and 30 cents a minute. Fring (fring.com) lets you use your Skype account, including SkypeIn, so you can receive calls too.
Turn the page to see how to turn it into a media center.
With Apple's Universal Dock ($50; apple.com), you can play video and music from your iPhone through a connected TV and stereo. Download movies and TV from iTunes or transfer them from your Mac, and install applications like Pandora and Last.FM for customized Internet radio.
Turn the page to see how to turn it into a music studio.
From vinyl scratching (MixMeister Scratch; free) to more cowbell (More Cowbell; free), the iPhone can provide just about any sound you're craving. One of the most versatile apps is MooCow Music:Band ($1.99), which gives you simulated piano, drums, bass, blues guitar, metronome and, of course, crowd noise. To get a little more utility out of your actual instruments, use any number of tuning applications, including Stay in Tuen ($4.99) and Tunic Guitar Free (free).
Turn the page to see how to turn it into a tool shop assistant.
Our pal Chuck over at Toolmonger has put together a list of five uses for your iPhone around the shop including the rather analog straight edge, and a digital level using the phone's built-in accelerometer and an app like Bubble Level ($.99). We'd add "calculator" to that list with the handy ShopCalc ($1.99), which can add fractional and decimal measurements interchangeably, and a more comprehensive unit-conversion app like Units (free), which handles everything from pressure to power.