Are you looking specifically at AVR? ARM works out-of-the-box with stable Rust.

I can really recommend getting a micro:bit board and following the discovery book [1].

There are a few other books in the embedded Rust bookshelf [2].

Otherwise, I wrote a bunch of sensor drivers and simple examples for several boards: [3]

[1]: https://docs.rust-embedded.org/discovery/index.html

[2]: https://docs.rust-embedded.org/

[3]: https://github.com/eldruin/driver-examples