TNeo is a well-formed and carefully tested preemptive real-time kernel for 16- and 32-bits MCUs. It is compact and fast.
TNeo was born as a thorough review and re-implementation of TNKernel v2.7. The new kernel has well-formed code, inherited bugs are fixed as well as new features being added, it is well documented and tested carefully with unit-tests.
You can read the article about it: How I ended up writing a new real-time kernel.
Currently it is available for the following architectures:
It is hosted at GitHub.
Comprehensive documentation is available in two forms: html and pdf.