OKCash is a Proof of Stake cryptocurrency that was released under the MIT licence.

Cashbery Coin's blockchain platform has a focus on enabling high-speed transactions with low fees. Cashbery's consensus mechanism combines elements of Proof-of-Work (PoW) and Proof-of-Stake (PoS).

Primecoin is a cryptocurrency based on finding prime numbers. Identifying prime numbers plays a central role in cryptography. Primecoin's unique Proof-of-Work (PoW) consensus mechanism is able to increase transaction speeds and improve energy efficiency.
The network searches for special prime number chains known as Cunningham chains and bi-twin chains, which are of interest in mathematical research.