While in it's infancy, there are already many mods beginning to pop up for Stardew Valley.
Mod API
Currently there are only two modification frameworks available:
- [[ http://stardewmods.com/resources/stardew-modding-api.5/%7CStardew Modding API (SMAPI)]]
- [[ http://stardewmods.com/resources/storm-modding-api.15/%7CStorm API]]
Both provide access to additional triggers inside the game.