WowAce

In-game theorycraft. Calculates actual damage/healing based on gear, talents and buffs.

Co-ordinated targetless Party and Raid wipe recovery. Evolved

A customizable casting bar replacement for TBC Classic & Classic WoW

Insanity resource tracker for shadow priests.

Speeds up triggering actions such as items or spells by triggering them on key/mouse down rather than release

Target Debuff monitor. Stacking aware, giving current and potential debuff status.

Buff reminders and more

A simple visual combat log with spell/skill icons for Classic WoW

ControlFreak

Mana regen rate display.

End of combat reporting for feedback on how your cast time was spent or wasted.

Displays a graph of the player's Mana regeneration

Out of Mana bar.

Displays your soulshards in better way.

Experiments in Mana/Regen Tracking

Manaburn

FuBar_MageFu

Simple addon that tracks internal cooldowns.

Templar is the ultimate Mage Assistant

Addon for knowing exactly when you get out of combat so that you can drink.