In the great tradition of tooting one's own horn, I'd like to suggest mutagen, a mutation testing framework for Rust. There has been some work since the last release and the next one is around the corner...
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I'd like to nominate datafrog by Frank McSherry
In the words of @nikomatsakis on his blogpost MIR-based borrow check (NLL) status update:
[the] analysis is now easily as fast as the existing Nightly analysis, thanks some smarter encoding of the rules as well as the move to use datafrog.
(emphasis mine)
Anything that helps the borrowchecker iterate faster towards NLL is a foundational blessing to the entire ecosystem, and deserves as much recognition as it can get! 
13 Likes
I would like to suggest my crate because I also need help with it :D.
It is a lib + cli to put csv files in a memory sqlite to allow queries over those files.
https://crates.io/crates/csv-query
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A lot of cool stuff this week. I am impressed
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Agreed! Thanks @nasa42 for kickstarting it with a host of good suggestions! (and also for tirelessly editing TWiR! )
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I'll cheekily nominate my own crate, paste, which is a pastebin anyone can run that's made to take on Gist, written almost completely in Rust (there are Ruby shims to call Rust code via sidekiq).
1 Like
I'd like to nominate Rutie (pronounced Rue-Tie) which is “the Tie between Ruby and Rust”. This crate is an official fork, and continuation, of both the Ruru crate and the ruby-sys crate.
2 Likes
cargo-update - keep all crates installed via cargo up to date (even git ones)
I don't know if it does qualify, it was mentioned in New Crates section almost two years ago but never was a Crate of the Week
3 Likes