Aether Link - Upcoming Website, for listing free, along with paid mods. Please note this site is still in beta.
Anamnesis - Allows clients to temporarily change their race, gender, looks, equipment, etc. in-game without actually making any changes visible to other players. Has the bonus of allowing users to create and load in their own poses.
Glamour Dresser - Newer repository. Contains listing of both paid and free mods.
Gshade - A heavily modified version of ReShade, with numerous improvements.
Heliosphere - Made to be used with Heliosphere Dalamund Plugin, allowing mods to be automatically updated.
Nexusmods - One of the oldest modding repositories.
Penumbra - Runtime mod loader, can be used while running the game.
ReShade - Reshade is a generic post-processing injector. ReShade exposes an automated and generic way to access both frame color and depth information and all the tools to make it happen.
Textools - FFXIV Modding Framework for both mod creation and use/installation, can only be used with the game closed.
XIVLauncher - Faster launcher for our favorite critically acclaimed MMO, with various available addons and enhancements to the game.
XIV Mod Archive - One of the largest repositories for modding, listing only free mods.