WowAce

Leveling guides for trade skill professions.

WF3sec

Shows a money overview for your current realm in the tooltip on the money in your bags

Displays friend notes in unit tooltips, at logon, and in /who results.

TwiCo

Collect data about you myth+ challenges

Simple library that handles multiple levels of logging.

Shows the minimum durability of equipped items on the stats frame.

Reminds you to Life Tap and Dark Pact

KC_Mobility

Right-click on minimap blips to open a targeting menu (out of combat).

Track any items you want in a tooltip

Handles the assignment, coordination, and announcement of many parts of the Lich King encounter in Icecrown Citadel.

TrackingInfo

Shows current/dot cast haste values

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

Retooled Professions

A popup menu containing user-programmable scripts.

LDB data source for reputation monitoring.

FuBar_MiniClockFu