Valve has confirmed that the newly released Workshop tools for Dota 2 will allow for easier creation and sharing of maps and modes in the MOBA sequel. Here's an explanation of some of the tools and features coming for the game:
Completely New Tools - The new suite of tools support creating and importing content for custom games. This set of tools requires a 64-bit version of Windows, Direct3D 11 compatible GPU, and opting into the Steam Client Beta.
Steam Workshop Submissions - This early version includes the ability to upload and distribute custom game modes through the Workshop. This new automated process allows players to subscribe to an author's custom game mode to automatically keep current as updates are released by the author.
Testing Custom Game Modes - This alpha release is focused on getting the tools to developers first. Currently playing custom games requires a 64-bit version of Windows and a Direct3D 11 compatible GPU. In upcoming future releases we will extend support to more systems (including 32-bit and Direct3D 9) and make it easier for players to download, find matches for, and play user created game modes.
If you know your Dota history, you'll already be aware that the game spawned from Warcraft 3, and was a community-made mode that took on a life of its own. Dota 2 and its peers are now amongst the most played games on the planet, and it seems fitting that a game that was born of a mod now has modding tools available.