There are 2 repositories under nix-overlay topic.
A package and module for using GNU Guix on Nix(OS).
A Nix flake to install Discord with Powercord
All Minecraft server versions packaged for Nix
NixOS overlay for Parallels Desktop tools
Nix overlay for node package managers, like pnpm, yarn and npm
A messy nix overlay with deemix-pyweb made for @Fomys
Overlay to add dark versions of Chrome and Chromium