Many of us have been there, a new phone comes out with bigger screen better specifications and what not, and we have to have it.
Regardless of how you upgrade, along with your new phone, usually you end up being stuck with your (not so) old one as well, leaving you wonder what you can do with it.
With new smart phones being released on a daily basis, it is not easy to sell them. Of course if you switch to top-of-the-line smart phones every month, your "old" phone is still a top-of-the-line model for most people, so selling it on sites like eBay/Craigslist shouldn't be much of a problem, but if you stick out the contract and upgrade period of most phone providers of 2 years (or a little less if they offer a rewards plan) it becomes a bit tricky to get rid of it.
You can take your old phone to a pawn shop or a game store, and trade it in for something else, but you will not get much for it.
So what else is there that you can do with your old smart phone.
Smart phones are multi-purpose devices. They run their own powerful operating system, and are more like small computers. They include features like camera's, wireless connectivity, and of course they are great little media devices, capable of playing video and music.
Of course your new phone contains the same (and usually more) functionality, but there are plenty of reasons to hold on to your old phone regardless, even without the need of having it tied to a cell phone company for voice and data services.
* Media Player:
If you look at popular media players like the iPod Touch 4 and the Samsung Galaxy Player, the functionality they offer don't differ much from an old Droid 1. They all play video and they all play music. Rather than picking up a dedicated media player for the gym, or even to entertain your kids when you go on a trip, you can just use your old phone for the same purpose.
* Apps and Games:
If you upgraded to a new smart phone, likely you stayed within the same device group. If you had an iPhone, you likely upgraded to a new iPhone, and of course the same goes for Android devices. Of course one of the reasons to stick to something you already had is familiarity with the device, but also to be able to use the apps and games you already purchased for your old one.
Here is the kicker though. Even if you upgraded, your old phone still has access to those apps as well. As long as you are using the same Apple ID or Google Account on both, you can use the same apps on both old and new. Sure, they probably run better on the new phone, and newer apps and games might not work properly on the old one, but still, the functionality you added yourself remains the same. Even if it is just a collection of Angry Birds games.
* Custom Roms:
While older smart phones often don't get updates to newer operating system versions, especially for the more popular ones, the "modding" community remains active for quite some time after. Groups like Cyanogen spend a considerable amount of time tweaking and customizing newer versions to make older hardware more useful.
*Rooting and Jailbreaking:
Scary words for some, and while you might have stayed away from these things when your phone was connected to a plan, you might want to dab into the customizing world with your old one. While most rooting/jailbreaking methods are perfectly safe, there are always chances that something doesn't go well, so using your old phone to learn rather than running the chance of bricking your new phone provides less of a risk.
My own use:
A few weeks ago, I ended up taking a Samsung Galaxy Player 5.0 for entertainment purposes on a trip. The main reason for picking that one over the rest of my gadgets was that it would take memory cards, and that it charges over USB, but in general use, the Galaxy Player ended up being less than what I was hoping for.
When the Galaxy Nexus came out, I upgraded from a Droid. The Nexus has a higher resolution screen, and of course comes with Android ICS, and has better specifications, but the Droid X has support for memory cards. Somehow it ended up in a drawer, and as a result I forgot about still having it, but for a future trip, I will definitely take the Droid X over the Galaxy Player anytime.
If you are in the market for a portable media player of some sort, don't forget to check your drawer. You might still have an old smart phone laying around that will do what you need and more. If you don't have one, rather than going out and picking up a brand new iPod Touch or Galaxy Player, take a trip to a game-store or a pawn shop and see if they have any decent smart phones there. It doesn't matter which network it was designed for (unless you want to have it as a fall-back device in case something happens to your main smart phone) so you could even get a cheaper one of the same phone that was released for a more obscure network.
At the time of writing, you can pick up a used Droid 1 for about $50, which, in my opinion, beats an iPod Touch in terms of games and apps, and has a slide-out keyboard to boot.
If you do decide to go for the used-route, don't forget to pick up a new battery (usually about $20) though.