WowAce

Keeps track of your top hits, heals, criticals, etc.

Some handy events that should exist in the default UI

LDB display of currencies, gold totals and session / daily / weekly statistics for all characters on a server.

Cartographer_QuestObjectives

Adds custom effects to your cursor.

A customizable casting bar replacement for TBC Classic & Classic WoW

Tracks skill and tradeskill costs and progressions, as well as trainer locations.

FuBar_PTReagentFu

Provides shareable notes and other information for your guild, party and raid community.

Database of FlightMaster locations for HandyNotes

SRA

Various libraries based on LCD4Linux, offering users lower-level UI customizations.

Simple quest item bar.

Static library of wow map data

A data broker display, that shows one block per plugin.

Switch macro depending on zones or BigWigs boss modules.

Litmus

tracks and share quests between your party

Doodle

Buffalo