List of Flash Gaming Engines — FlashRealtime.com

These are the libraries I personally consider highly useful for game development. Some of them are just for games – another are great complements. I am not going to write a lot about each of as they are mostly doing the same. Like collision detection, physics, tilemaps, optimized rendering, levels, sounds/volume, game states, score, some of them even multiplayer support and more. Better try demo games and see it in action.
(Link: List of Flash Gaming Engines — FlashRealtime.com)