WowAce

Square Minimap and more

SliceWatcher

WhiteboardNG

Used to visualize and change values of variables/variable-trees in game

Display the global cooldown around your cursor. (+ other stuff)

EnchantList

Adds a couple of graph displays to Skada.

Adds filters for Legion items to AdiBags

Resizes some default UI frames (GuildUI, LootFrame, RaidInfo, TradeSkillUI and TrainerUI) to show more lines

Adds a button to the quest completion interface which allows you to auto equips selected quest Item after completion

FuBar_RegenFu

Allows you to create icons, which can be customized greatly by user's input. CiR is more than just the usual cooldown tracker.

ActionCombat

Embeddable chat throttling library with traffic shaping and priorities

Library to help with querying unit talents.

Allows for easy congratulating when someone earns an achievement.

NabuFiveSec

Information display for Hunters.

Complain about crowd control breaks.

Keeps track of resurrection spells cast in a group