Platform Game Engine

The Platform Game Engine project is exactly what it sounds like, a game engine and toolkit for creating platform games. It seems very complete and feature-filled, with an advanced editor with all sorts of tools as well as advanced game features such as warps, doors and world maps. Long story short, if you want to create a platforming game without coding, this might be a good place to start!

Editing backgrounds in The Platform Game Engine.

Athenaeum

This one is a bit special, as it's not an actual game. But I found it interesting, so I decided to mention it anyway. Athenaeum is described as a libre replacement for Steam. That is, it is an application where you can download and catalogue games. You can download games to your collection, keep them updated or uninstall them. All downloaded games are displayed in a practical list and there are even screenshots and descriptions. All in all a cool concept that might help you discover new games to play or just make it easier to keep track of them. I should mention this seems to be early in development, but the main functionality is there and it does look really cool!