Smartphones have made the pastime of shopping more convenient than ever. Whether you need to compare some prices or keep track of your shopping list, all you need is a free app on your phone.

However, there's an entirely different side of shopping that these apps don't touch. Using your phone, you can purchase used goods from others and sell off your old junk. Here are some great apps for all the secondhand sales you could ever desire.

eBay

No list of secondhand sites would be complete without the leader of selling all sorts of stuff, eBay. Though the site started out built around auctions, the Buy It Now feature lets you instantly purchase any item you're interested in, just like Amazon. The eBay guarantee makes sure that you receive the item you paid for, reducing nervousness about scams.

The Android app provides everything you need to interact with the site, whether you prefer buying or selling. You can monitor items on your watchlist, keep up on items you've placed an offer for, see the latest deals, and check your messages. If you want to sell, the app lets you quickly snap pictures of your goods and list them.

Chances are, if you need it, someone probably sells it on eBay. Next time you need a replacement knob for your decade-old stereo, take a look on eBay. You'll be amazed at what you can find.

Download: eBay (Free)

Poshmark

Poshmark has become one of the biggest apps for buying and selling clothes. Aimed at women, it allows you to create a "closet" of new or gently used clothes you'd like to sell and encourages you to browse others' offerings. They advertise that you'll find prices up to 70% off retail, which adds up to big savings on fancy name brands.

The app lets you list items for free and makes the process of snapping a picture and creating a listing easy. Sellers set a price, but you can haggle a bit if you think they'll come down. Some digging could lead you to some incredible finds!

Whether you have a closet full of extra clothes or want to turn "flipping" thrift store shopping into a side source of income, Poshmark is worth a look.

Download: Poshmark (Free)

Shpock

Taking the award for the strangest name on this list, Shpock (the developers explain the name as an amalgamation of "Shop in your Pocket") focuses on local selling. The app markets itself as a digital flea market/classifieds section, allowing folks to sell in categories like Electronics, Sport, Home and Garden, and more.

You can sort your searches by distance, and the app prioritizes items from nearby sellers. Thus, if you don't want to deal with shipping goods or want to offload items quickly, Shpock is the app for you.

There are no fees for listings or transactions, and you can message the other party inside the app to arrange a meeting. Easy social integration means you can send off your new listings to Facebook and Twitter in a snap.

Of course, your mileage with this app will vary depending on where you live. If you're in a well-populated area, you'll likely find some great deals and all kinds of items to buy on Shpock. Those in rural areas might not see a lot of new content, but it's still easier than checking physical flea markets!

Download: Shpock (Free)

Carousell

Carousell is a lot like Shpock, except it connects you with buyers and sellers from both nearby and afar. Like the other apps on this list, you can create an account and start snapping pictures of your used items in minutes. You'll find common categories for browsing, and plenty of deals on gently used items of all sorts.

Unique to Carousell are Groups, which let you create a community of like-minded people. Whether you want to buy and sell with people in your neighborhood, people who have interest in a particular kind of item, or people of the same age, you can make a Group to keep track of them.

Download: Carousell (Free)

Don't Forget About Facebook!

If you don't want to use a separate app, you might already have the best shopping tool available installed on your phone. Facebook is a great place to exchange goods with local folks, as many communities and cities have big Facebook groups specifically for selling items. Perhaps few people in your area use the above apps, but a great majority probably use Facebook!

Your quest for finding great deals or selling your old junk will only be as successful as the number of people you can interact with, so have a look at the Facebook groups near you and join in!

Download: Facebook for Android (Free)

Download: Swipe for Facebook (a free light alternative to the bloated Facebook app)

Haggling is Easy with Android

There are many other apps that let you buy and sell used items, but they're quite similar to the above. For more, have a look at letgo and OfferUp. No matter which app you use, chances are you'll start selling without much trouble. Somebody, somewhere will want what you consider trash!

Or, instead of selling them, you could get creative and try repurposing your old electronic devices.

What are your go-to apps for buying and selling goods on your Android device? Tell us your best finds and success stories using these shopping apps down in the comments!

Originally written by Erez Zukerman on July 23rd, 2013.