OpenBazaar is the most popular global peer-to-peer decentralized marketplace. There are a few other.

BitBay - Relies on smart contract. The marketplace uses a double-deposit escrow system and rolling peg that controls liquidity and allows for price stability.

https://bitbay.market

BitMarkets - Like OB, Bitmessage network is used for posts and buyer/seller communication and Bitcoin is used for payments. Tor is used for user anonymity.

https://voluntary.net/bitmarkets

Like Syscoin there is NXT marketplace, supported payment method is NXT and products limited to digital goods only.

https://nxtplatform.org/what-is-nxt/marketplace

https://nxtwiki.org/wiki/Marketplace

BitHalo - Relies on smart contract, supports multi-currency.

https://bithalo.org