This is a thread for users to post resources (other than links to cart images, keep that in the respective thread) that may be useful to developers in this competition.
I'll start by directing those wanting art/sound/music assets to the Assemblee pages here: http://forums.tigsource.com/index.php?board=37.0
There you'll find a ton of resources in the Creative Commons license, so you can use them freely as long as you give proper credit and don't use them for profitable purposes.
Also, I'll quote Cthulhu32's post about his FamiEngine:
Oops, I was going to post this much earlier and Melly pointed it out, but I've been insanely busy the last few days.
I released a beta version of a quickie Famicom-like engine in C++ in Feedback a few weeks ago: http://forums.tigsource.com/index.php?topic=13261.0
Its totally free, written using SDL and OpenGL with the intention of making it easy and painless to make a Famicom like game.
Feel free to use it with your games, I don't know if I'll have time to finish the Shader NTSC support, but if I do I'll make it painless to integrate.
Remember that even if you choose a Famicom/NES cart, you're not bound by any restrictions. This is merely for those that wish to make something that looks like NES games.