Dignity is a stablecoin pegged to gold, that was developed by the company Cryptobontix. Each DIG token is pegged to the worth of 0.02445 grams of gold, which was worth exactly $1.00 at the time of the Dignity whitepaper.
Cryptobontix's portfolio of stablecoins are based on a partnership with bullion suppliers. Each individual token acts as a security on a 15-year convertible mortgage. The DIG token is pegged to the value of gold. Every year, 1/15th of the tokens can be redeemed for gold valued at around $1.00.
Cryptobontix does not actually own all of the physical gold. The company plans on spending its profits on acquiring the actual bullion that token holders will have the option of converting.

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.

Single Collateral DAI is a decentralized stablecoin that has collateral to back its value and an interest rate mechanism to stabilize its price. It is designed to be a digital currency with a stable value, that is pegged to the US dollar. (1 SAI=$1) MakerDAO is the decentralized autonomous organization that manages DAI and works to combat its price volatility. MakerDAO hopes to enable more decentralized applications by providing a stable digital currency whose value will not be susceptible to drastic fluctuations. The Maker platform itself, is powered by the MKR token, which is not a stablecoin, and has a volatile price because of its role on the Maker platform. In November of 2019 MakerDAO launched the Multi-Collateral Dai (MCD), which will eventually replace the existing Single-Collateral Dai, and will enable the company to offer a wider range of DeFi services.