Ravencoin is a blockchain created by the owner of Overstock.com. It is a use case specific blockchain for the declaration of ownership of digital assets. Ravecoin is a fork of Bitcoin, and was originally funded by Medici Ventures, a blockchain investment fund owned by Overstock.com.
Ravencoin's name is inspired by the use of Ravens in sending messages, and its blockchain is designed to carry statements of truth about who owns what asset. The developers created a new consensus algorithm called x16r to solve the problems of centralized ASIC mining. The algorithm is unique in that it consists of 16 different hashing algorithms whose order are randomly changed.

Stellar is a decentralized protocol for sending and receiving money, in any pair of currencies, directly on the internet. Stellar enables users to transfer money on their network directly, without banks, and without fees. It was originally created by Jed McCaleb, the founder of Mt. Gox and co-founder of Ripple.
Stellar has its own native coin called Lumens (XLM). All users must hold a minimum of 20 Lumens in order to ensure their authenticity and to maintain a wider distribution and free flow. Users must spend 0.00001 XLM in order to transfer fiat currencies. This provides the network with more liquidity for less popular currency pairs. Lumens are an inflationary currency with a fixed increase rate of 1% per year.
The network uses the Stellar Lumens Consensus Protocol (SCP). Unlike PoW or PoS consensus mechanisms, SCP relies on a Federated Byzantine Agreement (FBA), in which specific groups of nodes are chosen to arrive at transaction agreement. This provides the Stellar network with more decentralized control.
Lightyear.io, a for-profit entity of Stellar, was launched in 2017 as the commercial arm of the company.

BurstCoin is a cryptocurrency with a Proof-of-Capacity (PoC) consensus algorithm. Unlike most other cryptocurrencies, Burst's architecture uses a Tangle (similar to IOTA) instead of relying on a blockchain. It also utilizes ring signatures and other features, in what is called the Dymaxion. The Dymaxion implements layers of tangle-based lightning networks on top of the Burst blockchain. Each of these payment channels is opened in the form of a standalone colored tangle. Burst is also developing atomic cross-chain transactions (ACCT), that will allow for full decentralized trading between two cryptocurrencies.