Parity Technologies builds blockchain software in Rust. We're probably the only team in the world successfully reimplementing both Bitcoin, Ethereum and ZCash nodes from scratch. We only do opensource development, and are practicing Programmer Anarchy (https://www.parity.io/engineering-at-parity-what-its-like/) as our main development methodology.
We're currently focusing on Parity Substrate, our framework/toolkit for building blockchains in Rust, and are growing steadily.