Here's where jam participants can discuss game engines and development tools. Below is a brief list of free ones that I would recommend, some introductory resources to check out, and a list of well known games made with each in order to get an idea what the tools are capable of. I really only have recent experience with Unity, GameMaker, and Twine, so feel free to contribute any tutorials or info I might have missed, and ask questions if anything was unclear.

• Unity: The most popular game development tool, which is capable of creating both 2D and 3D games. Some C# scripting will likely be required, but a lot can be accomplished in the level editor alone, and with the help of the asset store.
Notable Games: Gone Home, Hearthstone, Cities Skylines, Ori and the Blind Forest, Cuphead Resources:Unity Beginner Documentation; Sebastian Lague Intro Playlist; A little pricey, but this kit available on the asset store is well worth the cost if you're interested in making first-person exploration games.

• GameMaker: A relatively beginner friendly tool specializing in 2D games. GameMaker features a drag and drop interface but can also be programmed entirely with it's own unique scripting language.
Notable Games: Spelunky, Hotline Miami, Hyper Light Drifter, Undertale Resources:Making A Game With No Experience; Shaun Spalding Tutorials;

• Twine: A tool used to create interactive narrative and text based games. While it can be used with no coding, CSS and JavaScript can be integrated for additional functionality.
Notable Games: Depression Quest Resources:Twine Wiki; (Twine is really easy to pick up and shouldn't require much reading to get started)

• Unreal Engine: Noted for its visual quality, and used in AAA and indie games alike, especially for first person shooters. While a lot of effort has been put into making the engine more accessible, it will still require some research and knowledge of C++.
Notable Games: Bioshock, Unreal Tournament, Mass Effect Trilogy, Life is Strange, Rocket League, Fortnite Resources:Unreal Engine Official Documentation; (I have zero experience with Unreal, so I'll let someone who does fill in the gaps here)

• RPG Maker: While very focused in its capabilities, specializing in JRPG style games, RPG Maker is also pretty straight-forward and easy to use. It requires no coding, but additional functionality can be added with custom scripts using the Ruby language. There are multiple versions, each with a free trial, but RPG Maker VX Ace Lite is a completely free version, which should serve the needs of this jam. Several of the paid versions along with some assets are also currently available via a Humble Bundle.
Notable Games: To the Moon, Lisa Resources: RPG Maker VX Official Documentation; (I haven't used RPG Maker for several versions so hopefully there's someone familiar with its more recent iterations.)

• Superpowers: I'm not very familiar with this engine myself, but it was recommended by Potatoes Are Not Explosive in the previous jam. It's a collaborative HTML5 engine that actually runs in the browser. If you set up hosting for it you can get google-docs style collaboration, which is not great for proper software engineering but it's awesome for game jams!
Resources:http://superpowers-html5.com

• Puzzlescript: An HTML5 based game engine designed for puzzle games. Recommended by Nina for those who don't want to get into too much coding.
Resources: https://www.puzzlescript.net/

• Bitsy: Also recommended by Nina, Bitsy is a grid based, retro-style engine that's works well for top-down adventure games.
Resources: http://ledoux.io/bitsy/editor.html