The Nix Packages collection (Nixpkgs) is a set of nearly 6,500 packages for the Nix package manager, released under a permissive MIT/X11 license. It supports a number of platforms (though not all packages work on all platforms):

On GNU/Linux, the packages in Nixpkgs are ‘pure’, meaning that they have no dependencies on packages outside of the Nix store. This means that they should work on pretty much any GNU/Linux distribution.

There is also the Nixpkgs Monitor which keeps track of updates and security vulnerabilities.