As auction sites like eBay have grown to marketplaces for full-blown store-owners, apps like Poshmark have become an increasingly popular way to sell your items. Posting your products on Poshmark is as easy as snapping a photo and filling out some details. Then, sit and wait for your product to sell! Of course, it's not just for selling your stuff. The app hosts "selling parties" nightly, where you can shop the closet of like-minded shoppers for specific brands, events, or even moods. Some sellers offer trades, as well, so you can swap items without exchanging a penny.