Whether you're looking to sell something, looking to buy something or are simply looking for a service, Selloby [Free] is probably the best way to do it - from your iPhone, at-least. Though it's currently still at its infancy, the service is much like a CraigsList alternative and somewhat like an eBay spinoff.
Once you download the application, you'll be prompted to make a free account, which only takes about a minute. From then on, after you select your location in the States, you'll be able to start browsing the potential plethora of things on sale. The application will also detect you location, only if you have location services enabled in Settings, but unless you were ever worried about battery life and decided to turn off your location services, you needn't worry about how to turn it back on.
Selloby has a list of broad categories available, which will then display all of the items for sale in your area. If you find something in particular that you like, it's easy to share on social networks (Twitter, Facebook), add the item to your favorites, or even follow it. You can further contact the seller to make an offer or find our more about the service/product being sold simply by using the button displayed on the product page.
Additionally, you're able to sell your own things using Selloby, which is extremely easy. If you've ever used Twitter before, the combination of hash tags and '@' signs is used for certain things. The same applies here, except you're using exclamation marks, '!', '@' signs and hash tags, '#' to describe whether you're renting, selling, etc., to say where your location is, and what the item is you're selling, respectively. After writing that, you can post a picture by either taking one or by choosing a pre-loaded one from the camera load; it'll soon be online available for everyone to see. Example: Selling #bike $165 @Atlanta
The world of Selloby isn't just limited to selling and buying. Nope, instead, you can also find a various amount of other things people are looking for or offering. Dating, jobs, and renting a place are just some of the other things that are up for grabs, if you will, in Selloby's huge database.
Selloby's user-interface is very well made. I did not once have an issue trying to navigate around the various menus and such, which is always a good thing when it comes to utilities like so.
It's basically a simplified version of any one of your favorite similar services, much worth the download. If you're looking to sell 'o' buy, then pick up Selloby on the App Store for free. It's easy to post what you're selling and to buy, so even if the relatively lacking user base doesn't bite on your product, you haven't really lost anything.