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.

STASIS EURO is an Ethereum-based stablecoin that is pegged to the Euro. Each STASIS EURO token is backed 1:1 with Euros held in a reserve account. The STASIS EURO was created by STASIS to power their tokenization platform. EURS can be issued in exchange for securities, which are purchased by STASIS’ liquidity providers. The EURS token is supported by an ecosystem of liquidity providers and exchanges.

Reserve Rights is an Ethereum-based stable token that is built on the Reserve Protocol. Reserve token will be initially backed by several other collateral tokens that are each tokenized versions of the US Dollar. The project has plans to transition to a collateral model that will not be pegged to the US Dollar.