The Rust Programming Language
by Rust Project
The official book — the best starting point for learning Rust from scratch.
OSDev Rust Wiki
Community wiki for writing operating systems in Rust — bootloaders, paging, drivers.
Related resources
Rust by Example
by Rust Project
Learn Rust through annotated examples covering core concepts and the standard library.
Rustlings
by Rust Project
Small exercises to get you used to reading and writing Rust code.