If you are looking for Multi vendor eCommerce platform like ebay,and if the seller want to sell their product you can try looking at these marketplaces

Amazon.

Etsy.

Rakuten.

Newegg.

Bonanza.

eBid.

Your Own Webstore.

or brisksale as suggested on the answer written by Ryan Speier.

But if you are looking to set up your own marketplace:

Let …