The Clothing Exchange is the best example of clothes swapping I’ve found in the online sphere. Users upload photos of clothes they want to swap and assign them a value between one and five buttons. You can then peruse database for items that interest you and make ‘swap requests’ for clothing of equal or lesser button value. There’s also a purchase facility if you aren’t looking to sell, and they host swapping events interstate (believe me, I’m doing everything I can to get one happening in Tassie!).
For more information you can find The Clothing Exchange here.