Namecoin is a blockchain-based DNS that allows users to register domain names with a ".bit" domain. Namecoin was the first fork of the Bitcoin protocol and it aims to remove centralized control over domain registration. It was the first cryptocurrency to use Auxiliary Proof of Work (AuxPoW) as a consensus mechanism,
where a child blockchain is dependent on the Proof-of-Work consensus of the parent blockchain. This allows for Namecoin and Bitcoin to be mined simultaneously, and when a new block is created on Bitcoin, it will also be added to the Namecoin blockchain.
Namecoin is a very important project that represents one of the best use cases of blockchain technology in protecting free speech and resisting censorship on the internet. It is powered by the NMC coin. The decentralized DNS provides more security from hackers and government intervention.

XinFin is a blockchain technology company that has developed the XDC protocol. XinFin's hybrid blockchain enables peer-to-peer contracts on a regulated payment infrastructure. Their goal is to create an open source marketplace platform that will reduce inequalities in global finance.
The XDC blockchain is built upon Quorum, a permissioned blockchain developed by J.P. Morgan. Quorum was developed as a layer upon the Go implementation of the
Ethereum protocol. XDC's consensus mechanism allows for new blocks be created in a two-step process. In the first step, the transactions to be included in the new block are voted upon by all participating nodes. In the second step, one node is selected as the leader or block maker randomly. The block maker node then creates the new block.
XInFin is powered by the XDCE token.

Ignis is a blockchain platform that is being developed by Jeluirda; the company behind Ardor and Nxt. Ignis is a child chain of the Nxt blockchain. Jelurida is developing blockchain platforms that will enable users to develop decentralized applications, and will be based on a parent and child chain architecture.
Ignis allows users to create child chains with specific features and to create tokens that meet their needs. This project is closely related to Ardor and Nxt.