nUSD is a stablecoin that is pegged to the UD Dollar. It was created by Havven, a decentralized payment network. nUSD has a dual token mechanism that provides stability. In order to generate nUSD, users must acquire Havven Coin (HAV) and lock it in a smart contract. 80% of their HAV holdings remain in collateral, and 20% of its value is generated in the form of newly minted nUSD. This collateral staking mechanism includes an incentive mechanism that rewards users with a portion of the transaction fees that are collected when nUSD transactions occur on the network. nUSD is currently an Ethereum-based token, but will soon be transferred to EOS.

Tether (USDT) is the largest stablecoin cryptocurrency. It is pegged to the US Dollar. (1 USDT=$1 USD) Each Tether token that is issued is backed by $1 USD that is supposedly held in reserve. Tether has been the subject of some controversy because they have failed to allow a transparent audit of their currency reserves.
Tether facilitate transactions between cryptocurrency exchanges at a rate that is fixed to the United States dollar. This allows traders to take better advantage of arbitrage opportunities. Tether was created by the leaders of Bitfinex, one of the largest crypto exchanges.

USD Coin is a stablecoin created by Coinbase and Circle. It's backed by USD (1 USDC=$1 USD), and is designed to be a stable digital currency that will fit within the trust and regulatory frameworks of the financial system, while still benefiting from the transparency and advantages of crypto powered networks. USDC is issued using the CENTRE open source framework and membership scheme, and it is available as a framework that multiple companies can leverage. Eventually other financial institutions will be able to become USDC issuers (and issuers of other fiat stablecoins - e.g. EURC, JPYC, GBPC), and customers will be able to tokenize USD and redeem USDC tokens in an open and interoperable ecosystem of financial institutions. A membership governance model for issuers will ensure that they meet technical, operational, regulatory, compliance and audit requirements.