Nethereum is an open source .NET integration library for Ethereum. It is designed to help developers easily integrate the Ethereum blockchain into their .NET applications. It consists of modular libraries for features that are covered are writing smart contracts, cryptographic wallets, DApps, and managing blockchain data.

Lamden

MetaHash is developing a blockchain platform for creating DApps. Their network has a multi Proof-of-Stake (PoS) consensus mechanism that is designed to increase transaction speeds and block formation times by using all of the nodes on the network.