Anton's OpenSCAD library
Because every OpenSCAD programmerdesigner has their own library.
As anyone with a Java background I recognize the authority of internationally viable namespacing. For that reason I refer to the parts in this library in my designs as se/antoneliasson/thing.scad and thus recommend that you install it into your local OpenSCAD library path like this:
$ git clone https://github.com/antoneliasson/antonscad ~/.local/share/OpenSCAD/libraries/se/antoneliasson
assuming that you are on a Linux system.
As this library is currently developed without much thought to backwards compatibility or stable versioning, you may instead wish to include it in your project as a git submodule. That allows versioning the library together with your project and update it (or choose not to) in a controlled fashion.
License
See LICENSE for everything but libraries in the thirdparty directory. Thirdparty libraries may have differing licenses. Refer to each library file's accompanying license file.