Know Your Tools
Feel free to download and play around with these pieces of software or explore the links provided before the game jam gets underway. You don't need to be a Unity guru or an expert in Creative Commons licensed materials, that's not what this jam is about. It'll just help to know where to find and the basics of how to use these things. Just don't go designing your game before the jam and then use the three days to polish up your prototype. These links are here to inform, not to help you be a dick.
Focus on the Basics
For this game jam our watchword is: KISSFGSYOHTFD, or Keep It Simple Stupid For God's Sake You Only Have Three Fucking Days.
Seriously though, we don't have a whole lot of time and you're working with people you might not know on a project you probably haven't thought a lot about. You are not going to be making a game, at best you will be making a prototype of a game. In other words, you will have time to make something demonstrating that the basic game mechanics you wish to create actually work. It probably won't look great, it probably won't be very long, it probably won't even work. But it'll be yours, and that's the point.
Because make no mistake about it, we're all going to fuck up a lot. Our games are going to be terrible and we'll be embarrassed of them. That's the goal, to make something terrible.
You will feel afraid, you will have no idea what you're doing, you'll feel like you're fucking everything up. All that feeling means is that you are currently participating in the Jam. So roll with it and fuck things up even more!
Unity is pretty much the be-all and end-all of free video game development software. Not only do indie studios use it, but developers like Electronic Arts have been known to use it in their web games. Almost everything you'll need to make a game is here, including support for multiple platforms.
Actual game developers have used this to make games like: The Room, Kentucky Route Zero, Temple Run 2, and The Guns of Icarus Online
Flash! It's not just to annoy you with terrible web design and make it impossible to watch movies on your iPhone. It's also very handy in making simple and not so simple games. Several popular games like Super Meat Boy got their start as flash games.
Actual game developers have used this to make games like: Machinarium and Super Hexagon
Unreal Development Kit
Hey you know that game you like? Like... literally almost any game? Yeah, it was probably developed using the Unreal Engine. The defacto game engine for several large AAA developers, Unreal is free to download and try out.
Actual game developers have used this to make goddamn near everything.
XNA Game Studio
Thinking of developing exclusively for Windows? Microsoft has an app for that. Wait...
Microsoft XNA Game Studio allows you to use Visual Studio to create games for the PC, Xbox 360, and Windows Phones. You know, if anyone actually has one of those.
Actual game developers have used this to make games like: Magicka, Terraria, and Dust: An Elysian Tale
Stencyl is a sexy piece of software that lets you develop iOS and Flash games. It has a sleek, snap-together functionality that skips past all that messy coding and lets you make a game like you're making a scene out of Lego.
Actual game developers have used this to make games like: Kreayshawn Goes to Japan, Traitor, and Gyossait
Torque comes in two versions. Torque 3D, which much like Unity allows you to create a variety of 3D style games, and even comes with a premade game to use as a tutorial. Torque 2D is... uhm, the same. Except for 2D style games. Pretty cut and dry, really.
Actual game developers have used this to make games like: Penny Arcade: On the Rain-Slick Precipice of Darkness Episodes One & Two, and Swarm.
Twine is a tool that helps you easily create a text adventure game. There's even an easy step-by-step tutorial.
GameMaker is well... software that lets you make games. It's got an easy to use drag and drop interface, and is available for both Windows and Mac. There's also a lite version that's free to download.
Actual game developers have used this tie make games like: Barkley: Shut Up and Jam: Gaiden, Immortal Defence, and Dustforce.