Handmade Math is a simple, easy-to-use math library for games and graphics programming. It's a single header file, so it's easy to include in your project. It is fully compatible with C, but if you're using C++, you'll get operator overloading as well. The types are plain old data, and there's no object-oriented madness in your way. It's just math!
Handmade Math has support for vectors, matrices, and quaternions. It supports all arithmetic operations for those types, plus common graphics features like projection matrices and LookAt.
Handmade Math is under active development, so if you have any suggested features or improvements, please make an issue on the project's GitHub repository.