The most obvious option is to sell your old iPhone to a friend or online. Cautious sellers should stick to sites that offer some protection like eBay. There is an entire section on eBay for iPhones and they offer a buyer protection plan. Craigslist is a great local option. Just meet in a public place and take cash only. Be wary of any buyer that you can't meet face-to-face. Also, don't forget to wipe all of your data with a service like ReCellular.
If your iPhone has become your third arm, it might be a good idea to use your new iPhone for calls, emails, text messages and social media only. Keep the old phone around for everything else nonessential, like an iPod, flashlight, game center, eReader, cook book, language tutor, subway map or whatever app you use.
Credit: Apple/Ness Computing
Turn it into a home stereo
Another great option for old iPhones is to wipe out all of the apps and data and use it only as an iPod at home. Plug it into a Bose or iHome system and always have music playing without annoying interruptions from phone calls or text messages. Connect to Wi-Fi and use apps and stream music from Pandora or listen to live news shows on the National Public Radio app.
Turn it into art
Technology has been an interesting addition to mixed media art. Modern artists have incorporated televisions, typewriters and stereos into their installations as additional layers. There's no better way to worship your old iPhones.
Give it to your kids
If nothing else, give your phone to your kids for endless hours of peace and quiet. Load the iPhone with kid-friendly games and let them have a blast. Just be sure wipe unwanted files and set restrictions in general settings. This allows you to set a password to limit access to features on the phone.