WowAce

Lists and/or reminds people missing flasks or food buffs at every ready check.

ERP

Assistance for the Ra-den encounter. (Unstable Vita order, ball kill order)

Shows a countdown bar for the duration of auras (e.g. HoTs, DoTs)

Broker launcher that switches specializations when clicked. Also hides spell learned spam.

Never forget which one in that 5-mob pull casts what spell again.

Animated target indicator

Shows who controls Wintergrasp and the time until the next battle.

Fancy up the PlayerPowerBarAlt frame

Small addon to copy chat lines.

Tracks Black Market Auction House auctions.

Improvements to the standard Blizzard Eclipse bar for balance druids. Use /ebp for the config screen.

Shows loot information in item tooltips

NielasAran

Collects and displays census information. This AddOn is licenced under the GNU GPL, see GPL.txt for details.

Adds 3 indicators to each side (top, bottom, left and right).

A helper addon for the achievements "Let It Snow", "Fistful of Love", "Shake Your Bunny-Maker", "Check Your Head", and "Turkey Lurkey"

Denial2

"Shows Call To Arms status in an LDB data provider."

What did you just loot?