Mostly Open Source Game Engines . . .
In our work we are investigating what we need to build on our own, and what existing tools of which we might take advantage.
This is a nice big list of game making tools; the many 2D Platfom game engines are delightful to review.
Open Source Games and Tools
Free, Open Source Game Developer News
HTML5 Game engines
– Make games! No programming required. Free to use but pay if you make more than $5000.00 on the game.