WowAce

Paints your known blueprints red.

FuBar_GemWatchFu

A library that maintains a cache of items and their types.

FuBar plugin for ItemRack v2.2+

A customizable casting bar replacement for TBC Classic & Classic WoW

Hold a key to temporarily center and magnify the Minimap.

vChat

Profession launcher objects for any Broker display

Party and Raid roster library - one library for any group

Adds Debuff Highlighting to oUF.

Replaces the SkadaAbsorbs module with one that acts more like SkadaHealing, but includes shields.

Adds AFK status to Grid frames.

API for AceConfig-3.0

Hunter pet manager for any DataBroker(LDB) display.

Gives equipped and overall iLvl to indicate the quality of a character's gear.

Destruction Warlock priority module for clcInfo -- Maighurl

Lute

cyCircled_GoldOrbs

Adds tooltip for debuffs (and other things? you found out: no).

Shift-clicking on a user name in chat shows a tooltip with their whois information.