The Binding of Isaac blog has details on the upcoming Afterbirth DLC for the action/adventure game (thanks Eurogamer). Some of this takes a creative approach to creating intrigue with heavy redaction, but part of it is a straightforward announcement that this will include various editors to create mods for the game. Here's that part:

Afterbirth † will include a player/user-friendlier Room Editor, Animation Editor and Lua support. You’ll also be able to edit the item pools.

Room Editor: The Room Editor, will allow you to design your own rooms without hacking the game. This includes rocks, blocks, TNT, holes, chests, enemies and just about everything else Ed has access to.

Animation Editor: the Animation Editor it’s just exactly what it sounds like, you’ll be able to externally create your own new art, nightmares etc, then import those files into the animation editor to bring it to life and appear in the game. hashtag=fun

Lua Support: This might be the single biggest thing that will really allow you to go crazy in terms of modifying the game. With full Lua support you can create new enemies, items and effects and make a whole new Isaac or–hell, even an entirely new game that ISN’T Isaac.