WowAce

KivinSpamGuard

Save and send chat messages to many channels. Allows quick item and profession linking within your messages.

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

Combat Alert

Helps with interrupt notifications and announcements.

Adds achievement reminders to BigWigs

ezIcons

Add in keybindings to place raid marks on mouseover, or the target if there is no unit being moused over

A death track window for Recount

"Your quest log is full". How many quests do you have in your log?

Langoustine

KC_PlayerFramePlus

FuBar_TraxieFu

Vox

eeMon

iTargetingFrames

Allows custom-triggered boss mod timers to be created

Makes it very easy to collect rare battle pets.

SQL-driven database system for Lua

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