ieee802154 - Rust implementation of the IEEE 802.15.4 standard.
I can't believe this crate has never been cited nor is used much more : cargo-readme.
It allows you to, I cite from its README :
Generate README.md from doc comments.
[It] extracts documentation from your crate's doc comments that you can use to populate your README.md.
swc - Super-fast JavaScript to JavaScript compiler written in Rust.
shellfn: Rust proc macro for easily and safely use shell scripts in rust
Makes sense as the readme feels a bit duplicated. Although in my crate I currently have the README.md set as a generic thing. I also seen some crates using it for release notes.
mpmc-scheduler round-robin mpmc work scheduler
Inert of course. 
Battery, a cross-plattform library to retrieve battery information.
multi_try: safely combine Results -- ergonomically return multiple errors from validation.
psd - A Rust API for parsing and working with PSD files.
swym - efficient transactional memory in Rust.
prettier assertions https://crates.io/crates/pretty-assertions
looks interesting
@mark-i-m: Yes it's really nice but has already been crate of the week in issue 175:
https://this-week-in-rust.org/blog/2017/03/28/this-week-in-rust-175/
validator: simple validation for Rust structs inspired by marshmallow and Django validators
slice-group-by a crate that provide an efficient way to iterate over groups in str and slices. Useful to create tokenizers.
copyless - library that helps putting values into Box or Vec without memcpy instructions generated by the compiler.
cargo-call-stack: Whole program static stack analysis
luster: An experimental Lua VM implemented in pure Rust.
safety-guard: Provides a #[safety] attribute to generate a corresponding doc entry and a debug assertion if a constraint is specified.