Synaptic!

Chocolatey NuGet is a Machine Package Manager, somewhat like apt-get, but built with Windows in mind. It is built on top of NuGet command line and the NuGet infrastructure.In terms of updates, it allows you to update nearly everything on your machine with a few simple keystrokes.

Apt (for Advanced Package Tool) is a set of core tools inside Debian.

A software manager for the Linux Mint operating system to easily install new applications.

One of the great things about using open source software is the frequency with which bugs are fixed, security holes are patched, and new features are added. Ubuntu includes a very convenient update manager, which checks the software repositories for updates, and alerts you to install any new versions found. However, if you are annoyed at constantly upgrading, you can follow this guide to tweak the settings of the manager: Navigate to the Software Sources control panel. Under your “System” menu, select “Administration”, and select “Software Sources.” You will be prompted for your root password; once the window opens, select the “Updates” tab: »

App Grid is a new lightweight Ubuntu Software Center alternative that tries to make application discovery easier by using a grid view which includes app screenshots and ratings.

Nix is a powerful package manager for Linux and other Unix systems that makes package management reliable and reproducible. It provides atomic upgrades and rollbacks, side-by-side installation of multiple versions of a package, multi-user package management and easy setup of build environments.

Octopi is a GUI package manager built on QT that makes using both of the Arch/Manjaro prime terminal package managers - pacman & yaourt - simple point & click operations.

OneGet is a unified interface to package management systems and aims to make Software Discovery, Installation and Inventory (SDII) work via a common set of cmdlets (and eventually a set of APIs). Regardless of the installation technology underneath, users can use these common cmdlets to install/uninstall packages, add/remove/query package repositories, and query a system for the software installed. Included in this CTP is a prototype implementation of a Chocolatey -compatible package manager that can install existing Chocolatey packages. »

RubyGems.org is the Ruby community's gem hosting service. Instantly publish your gems and install them. Use the API to interact and find out more information about available gems.

Ubuntu Sources List Generator is a website where you can generate a sources.list file with a lot of useful repositories.