I like these companies a lot for they appear transparent, leading me to trust them.
Ferrous Systems, which offers Rust consulting and training, also does a lot for the language in the embedded domain by running Oxidise. That, combined with having Jorge Aparicio work for them, makes them the most visible name in that domain for Rust. I am also excited for the effort in helping Rust get to be certified to be used in Safety Critical systems, Sealed Rust.
Mullvad, which offers a VPN service, develop their tools in public (open source), and Rust features a lot in those. Reading through their site leaves me impressed about how serious they are about security and privacy.
Cloudflare, which offers various internet services, offers many of them without a fee. The one I use is the DNS service, with a promise of speed and privacy. Also impressive is their blog posts, which are both detailed and numerous. A number of them have to do with Rust, for they use the language to develop some of their tools.