When choosing an NFT Marketplace you want to choose one that fits what you are trying to buy or sell and what will give you the best most visibility. Here are 4 popular options.
OpenSea

OpenSea was created in 2017 and was the first and is currently the largest NFT Marketplace out there. With over 1.7 million active users and over 80+ million NFTs on the platform, it dwarfs its competitors. OpenSea supports the following currencies Ethereum, Polygon, Solana, Klaytn. They support everything from Photography NFTs, Music, Trading Cards, Art and more. OpenSea also supports lazy minting which means when you list an NFT you don’t have to pay any fees until it sells. Opensea is one of the most user friendly options.
Rarible

Rarible was created in 2020 and is a community owned marketplace. You can buy or sell NFTs from Art, Photography, Music, Sports, Games and more. They support the following currencies Ethereum, Tezos, Flow, and Polygon.
SuperRare

SuperRare launched in 2018 and is a more exclusive marketplace where you have to apply to get approval. Not everybody can sell NFTs on this marketplace since they believe in a more quality approach to NFTs. SuperRare is built on the Ethereum platform.
Solanart

Solanart was created in 2021 and is built on the Solana platform. It is the first marketplace on Solana. It supports NFTs that you can buy and sell. This is a popular option if you are using Solana.