It's the end of summer and fall is peaking its chestnut-colored head around the corner. It's asking, what will you do with those bright florals when the leaves start turning muted shades of amber? But if you think you're going to unload a few summer dresses right now, you're doing it wrong. Even the best summer wear will have trouble selling when everyone's looking to get rid of their own.
Steal a trick from retailers and stock your storefront with what's seasonally appropriate — maybe your unwanted fall clothes from last year. Sure, fashion changes year to year, but you likely have some basics that held strong but just don't fit the same as when you first bought them, and still are in good shape.
See also: 9 Excellent Apps For Discovering New Things
Meanwhile, slip those summer clothes into an airtight storage container and let them resurface next May, when you'll make a killing.
In shopping mode? Grab some brown booties or a chunky sweater in your size while it's still available.
Twice takes a hands-on approach. You send them your clothes (you can print out a shipping label from the site) and they measure and photograph everything to sell to other users. The site has a fun calculator that will tell you what to expect to earn from a type of item (such as jeans) from a certain brand (7 For All Mankind). You have less control over the process than you would with a site like Threadflip — but you are ensured to clean out your closet.
If you're shopping for quality brands with nearly unused clothing, this is your site. Thredup does not allow users to sell directly to each other, but acts as a consignment store, and buys directly from users, then resells to the community. The site has guidelines on what brands it will accept, and what amount of wear. Notably, it has sections for kids, so if your children are growing fast it might be a good place to make a buck off that outfit they only got to wear one time.

Poshmark's model is a bit more social in the sense that you can follow someone else's closet. Is it creepy that, if you buy a dress from someone that fits great, you might continue to buy from them because apparently you have the same size and style? I'm not sure, but it could prove an efficient shopping method. On each Poshmark sale, you keep 80% of the sale price — but Poshmark sends you a shipping label, so you save money there.

By far the most known of fashion resale sites, Threadflip is scaling quickly. The search categories are detailed, which makes finding something specific, easy. For example, I know what size of Steve Madden shoes fit me like a glove, and I can quickly see all the Steve Madden in my size on Threadflip — which there are many — and even narrow it down by shoe type or color. If you're looking for something specific you might just find it (which, in Goodwill and other used retail stores, is often unlikely). Threadflip lets you keep 80% of each sale.
With a fair amount of designer clothing, bags and wedding attire, Tradesy is a great place to shop. You can browse by brand and I was surprised to see how much lululemon products were on the site, since fitness clothing is definitely not the first thing I'd think to resell (but sometimes you realize you have the wrong size when it's too late to return, I guess). Tradesy takes 9% of each sale — much less than other sites.

When it comes to social, mobile apps, Copious is the most targeted — you'll upload a photo of the item you want to unload, add a bit of text and invite friends to check it out ... via text message. Clearly, the play here is to get good, trusted friends sharing items. The flexibility comes in that you can use it for any type of item — shoes to lampshades to cars. If you're cleaning out your closet it might be a quick way to ensure your items don't go to waste when they'd be greatly enjoyed by someone you know.
There are most likely a few items in your closet that you don't want to get rid of, yet you never wear them. Sometimes, they have sentimental value. If that's the case, a site you should know about is Project Repat. The company will take your old T-shirts and transform them into a blanket, size of your choosing.
Image: Flickr, julierashell