Openbazaar which has been going for a quite a while but you never really hear much about it. It's not a site, it's a client you run yourself so the chances of being scammed are vastly lower. I don't know how busy it is these days but it's worth checking out. Though reading up about Satoshibox I can't quite figure out what people sell there other than scammy shit.
There are few youtube video that buyers could bypass the satoshibox without paying, this might be the reasons why the owner of the site become scammed and this is like the same as selly.gg.
Anyway, I just want to add more site as an alternative for satoshibox.
The alternative that I know you can use is https://bitify.com/ and use an escrow or use some payment gateway like bitpay or a payment gateway from coinbase is a good alternative.