Plugins and mods
Dalamud plugins add features to Final Fantasy XIV while it runs. You install them from the Plugin Installer, which the /xlplugins chat command opens once the game is started through XIVLauncher.
Each plugin is built for one Dalamud API level. When Dalamud moves to a new level, plugins built for the previous one show (outdated) in the installer and stay off until their authors update them.
Mods from Nexus Mods replace the game’s models, textures and sounds on your own client and are loaded with Penumbra or TexTools.
ZeeDees, bring the Zs to your Ds!
Pick titles you want in a title roulette.
Exports your current class hotbar into text. Allows imports too!

Upscale of the Summer Indigo Shirt to the Bibo+ body, all sizes included.
Game items
Summer Indigo Shirt
HD upgrade to Sch and Smn pets

Upscale of the Faire and Shisui Jois to the Bibo+ Body, all sizes included.
RequiresTexTools
A 2D pool game inside Final Fantasy XIV.
Help you record duty and who you met.
Import map coordinates to echo chat.

Easily clean out your Glamour Dresser.

Automatically finely scales the game UI by resolution.

Attempts to reduce or eliminates(Ultra) shimmering caused by grass.
Requires
Save and load actions into hotbars without taking up extra job hotbars.
This is still mostly a dev tool for debugging, but people like it?

Push notify to your device when your duty is ready
Shows an overlay and/or sends alerts when your held currency items (or non-currency items) match configurable rules. A spiritual successor to CurrencyAlert.

Upscale of the Southern Seas Skirt to the Bibo+ Body, all sizes included.
RequiresTexTools
Game items
Southern Seas Skirt
Upscale of the Spring Bottoms to the Bibo+ Body, all sizes included.
RequiresTexTools

Finally got the squat working so now I can give out the nice miqo'te groundsit animation pack that sways the tail and wiggles the ears

This is a ReShade preset that will greatly enhance your visual experience without putting a strain on your frame rate.
RequiresReShade

Automatically rename your screenshots with character and location info.
Give your UI that premium, acrylic look upgrade. Because Eorzea looks better with some blur.
A classic arcade game.
Easily get general and role-specific hints in duties.
A mod that calculates what you can do with what you have.

Upscale of the YoRHa Type-52 Bottoms of Casting and Healing to the Bibo+ Body, all sizes included.

Just a male miqo'te set of animations that modify their chairsitting animations to have some tailsway and earwiggles
Tobii and Eyeware Eye and Opentrack tracker support for FFXIV

Upscale of the Bunny and Bunny Chief Tights to the Bibo+ Body, all sizes included.
RequiresTexTools
For when you want to spend time fighting the boss, not fiddling with waymarks.

Upscale of the Skyworker's Singlet to the Bibo+ Body, all sizes included.
RequiresTexTools
Game items
Skyworker's Singlet
Upscale of the miqo'te Hempen Camise to the Bibo+ body.
Game items
Hempen CamiseKeep on top of new items.
Total control over where to put your hotbar slots.

Upscale of the Craftsman's Singlet to the Bibo+ body, all sizes included.
Game items
Craftsman's SingletI'm ready, I was just alt tabbed!

Upscale of the Neo-Ishgardian Top of Fending to the Bibo+ body, all sizes included.
Game items
Neo-Ishgardian Top of FendingNever think too hard about your bags again!

I promised I'd do this...It made the front page of the reddit so I have to make sure the people can have it.
Requires

Upscale of the Obsolete Android's Halfrobes of Casting and Healing to the Bibo+ Body, all sizes included.