WowAce

Estimated time until current target will die.

Fires events whenever a raid member "fails."

Displays the time remaining before your (temporary) pet is dismissed.

LDB data source for Combat Tracking

Mutt (Macro Update Target Tool) provides slash-commands that can patch the predefined targets in your macros.

Gathers statistics on certain chance-on-use spells, also known as procs.

Combat log evolved.

Food/water macro generator

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

Desesperated announcing to clearly show the skillings of act inplay.

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

Tracks the Blood Shield for Death Knights.

Death reports

Monk Brewmaster/WindWalker Priority and Buff/Debuff Tracking Tool

Alternate Rune Display

Helps you decide which ability to use next according to priority you set

DotDotDot

A clone of the FailBot mod. Announces raid member failures such as "Player1 fails at frogger"

Entertaining kill-shot notification.

KillingSpree