I like Overstock, and have gotten some great thing for my new house there, but watch what you buy, you may be able to find it for a better deal elsewhere.
I like how you can order items online and they can have them ready for you to pick up at the store. It saves time. Their ship to home service is wonderful, too!
I have been using thredUP for quite a while now, but was recently charged a more for the shipping and handling of their clean up bag that what my items were apparently worth. Since they give you very little for what they do accept, your payout may not even cover the cost of shipping. I probably will not be sending them items to sell again.
Tip for consumers: I like buying from thredUP, though their size assessments run small, just as a note.