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.

The Cardano blockchain is a 3rd generation blockchain platform that was designed with a collaborative peer-to-peer review system, It aims to improve upon prior blockchain systems to enable larger and more sustainable uses of the technology.
Cardano was built with a governance model that is based on collaboration. This allows the platform to evolve quickly and adapt to the changing needs of its users. Unlike many other blockchain projects, it also installed a treasury system to fund the ongoing development needs that may arise as it moves forward.
The Cardano blockchain uses a unique proof of stake algorithm called Ouroboros and has a protocol that consists of two layers, a settlement layer and a control layer. The settlement layer is designed to perform accounting functions, while the control layer is tasked with running smart contracts. The platform tries to balance the privacy concerns of users with the requirements of regulators in an effective way.
Cardano uses the Haskell programming language and is fueled by the ADA coin

Blockstream is a private, for profit, blockchain technology company, that has played a key role in helping to develop, and fund, many of the key features of the Bitcoin Core platform. Blockstream is focused on developing bitcoin applications and has raised significant funding from several large investment funds. The company also employs several developers that are very influential within the Bitcoin Core development project. This, as well as being of Bitcoin's largest donors, has led to some criticism about conflicts of interest.
Blockstream is developing a number of Bitcoin applications that are intended to encourage adoption and improve transaction times on the bitcoin network. Their primary focus is on Sidechains, which are are extensions to existing blockchains that improve their functionality. The company is also working closely with industry leaders to create the Bitcoin Lightning system that will support higher trading volume and faster transactions on the bitcoin network. Blockstream is also developing a data feed, satellite network, and other applications that they hope will make blockchain more accessible.