WowAce

Always shows the Blizzard Raid Frame

Open those clams (and other containers)

Allows you to set up raid icon markings for all kinds of stuff.

Blocks all whispers except from people in your guild and friends list.

AutoMagicly clicks though Daily Quests, and Turns them In.

Add lines to ore and gem tooltips that show prospecting sources/results.

Allows customisation of login/logout system messages.

Scan for rare mobs so you can find them and their loot

Constructs a SimC export string for an item without equipping it

Show item levels in the character frame

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

Show a rough range indicator

Draws 3D portraits for main units that can be moved or resized at will.

Filters unimportant Buffs.

SimpleBar

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

SimpleChatMods

Provides cooldown timers for abilities you want to track

SimpleDrumAnnounce

A simple range indicator for optimizing Halo damage.