I would like to nominate the rust seL4 crates that are funded by the seL4 foundation. This series of crates provide an official way to run no_std Rust applications on top of the seL4 microkernel, providing unparalleled security, especially on embedded devices. I am a user of these crates and have found them very pleasant to utilize. They provide a lot of useful abstractions and users can select different crates to select how high-level of an abstraction they want to use.
Examples are provided that show how to utilize a number of the crates.