WowAce

Small addon to copy chat lines.

Hunter 'Misdirection' activity and cooldown monitoring for raids/groups. 'Readiness' aware.

Keeps track of honor, PvP statistics, BG Marks, and Arena points.

FuBar_PetInFu

Adds aggro coloring to oUF.

Provides information about the player's bodyguard.

LFD status via a DataBroker display rather than the minimap.

Adds indicators to the sides of Grid frames.

Reminds you if your flask/elixir and/or Augmentation Rune and/orfood buff is about to expire or has expired

Enhances the StackSplitFrame with numbered Buttons, a '1-Click Mode' and a 'Auto Split Mode'.

Note + rep tracking for players, with guild data sharing.

Adds pipes which can control arbitary other statuses (like toggle status on key or "in combat"-state).

GirlFriend

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

Sets you to DND when you fight a boss, and some other crap.

Adds 3 corner indicators to each corner of the Grid frames.

Advanced Chat Filtering and Spam Blocking Addon

Adds a confirmation dialog when crafting Bind-On-Pickup trade skill items

Group interrupt cooldown tracking.

Automatically sells low quality gray items and selected white items to the vendor.