I want to nominate mitsein, which is a crate that provides non-empty collections.
It has both the generic NonEmpty<T> wrapper as well as aliases like Vec1.
It has macros for constructing non-empty collections.
It supports more collections than any other non-empty crate I could find. It has feature flags for popular crates like serde, schemars, smallvec, itertools and others. I've been looking for a crate like this for a really long time, and I finally found it.
The author is also really active, the library is very well documented, and there are constant commits to it. When asking questions in his issue tracker, he gives long thought-out responses and takes lots of care. I want it to be featured in crate of the week!