WowAce

WF3sec

AltClick an item in your bag to add it a mail, auction, or trade frame, and alt-click to buy a stack if reagents.

PreferredItems

Clean looking square minimap with many options.

Quest helping: fetching items to use, that sort of thing.

EnhancedLFG

RotLatency keeps track of your reaction to cooldown expiration.

Sets the DND flag, when are in combat.

Meeuuuh

Automatically invites player from templates.

Saves and restores your action bars.

Test whether the player can really dispell a buff or debuff, given its talents.

TextSpy

Replacement for the default nameplates.

Cryolysis

BigTrouble

Displays info about who rolled Need/Greed/Pass on items that are currently rolled for

ViewAddonMessage

FuBar_NinjutFu

FuBar_RicoXPFu