AS3isolib

FlashPunk

A free ActionScript 3 library designed for developing 2D Flash games. It provides you with a fast, clean framework to prototype and develop your games in. This means that most of the dirty work (timestep, animation, input, and collision to name a few) is already coded for you and ready to go, giving you more time and energy to concentrate on the design and testing of your game.

StarlingPunk

StarlingPunk is a framework built on top the Starling library designed to add structure and organization to your 2D game projects. It’s perfect for rapidly prototyping ideas and promotes code reuse between projects. As you may have been able to tell from the name, StarlingPunk is heavily inspired by the popular FlashPunk framework, although its not a direct port.

Pixelizer

A component based game engine for AS3. Master version is currently 0.4.3. Please note, the dev branch is currently under heavy development for 0.5 and should be considered unstable. There will be a few breaking changes.

Tetragon

Tetragon is an Open Source cross-platform game engine used to develop games and applications for the web, desktop and mobile devices. It is written purely in ActionScript 3 and comfortably allows to write source code once and deploy builds to several different target platforms. Unlike most other Flash-based game engines and frameworks that allow you to develop a specific type of game or that provide a subset API to support game development, Tetragon provides a complete foundation with that any type of game can be developed, incl. resource management, debugging facilities, multi-locale support, layered extendability, a game-oriented data structure, and a lot more.