I just created: https://github.com/nix-community/nix-environments
For some projects it is non-trivial to get a minimal develop environment that work with Nix/NixOS. The purpose of this repository is to share shell.nix expression that help to get started with those projects. The goal of the project is not to build or package those projects (which is often even harder) but to document the build requirements.
In an ideal world we could maintain those files upstream, however not all projects are accepting shell.nix files in their source tree.
If you also want share your setups for some projects you work with, this is the right repository.