Blacksmith 2D
Godot Engine
RPG Maker
MonoGame
FlatRedBall
AppGameKit
HaxeFlixel
ct.js
EverDev
Blacksmith 2DI recently needed a website and they were able to deliver in 13 days, I got a link to a trello board where i was able to submit requests immidiately!
Godot Engine - Feature-packed 2D and 3D open source game engine.
RPG Maker - Make your own PC game with RPG Maker. Our easy to use tools are simple enough for a child, and powerful enough for a developer. Try it free today!
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.
FlatRedBall - Cross-platofrm 2D game engine using C#, focused on developer productivity, transparency, scalability, and ease of use.
AppGameKit - AppGameKit is a game development platform for mobile devices.
HaxeFlixel - Create cross-platform games easier and free. All with one codebase.