Entropic - Federated package registry for anything.
Topgrade - Upgrade everything.
Repology - Monitors a huge number of package repositories and other sources comparing packages versions across them and gathering other information.
Spack - Flexible package manager that supports multiple versions, configurations, platforms, and compilers.
rebuilderd - Independent verification of binary packages - reproducible builds.
dripip - Opinionated CLI for continuous delivery of npm packages.
PRIVJS - Implement access control to your npm packages.
pkgsrc - Framework for building third-party software on NetBSD and other UNIX-like systems, currently containing over 22,500 packages.
Awesome Package Manager - Package manager resources.
ossmalware - Attempts to use dynamic analysis to find malware hosted on package managers.
UPM - Universal Package Manager - Python, Node.js, Ruby, Emacs Lisp.