WowAce

Auto sizes frame layout depending on group/raid size or predefined zone data

TradeBar

Speed plugin for any DataBroker display.

Add-on that shows which battle pets can be farmed this week

Lists Pots and Herbs you got on all chars and allows you to specify color coding

StatStain

Keeps a list of all items you want and shows how much you need.

Displays a reliable cooldown timer for the Shaman Ascendance ability

Displays bars depending on your professions

Keeps track of time played and rested XP across your characters.

Shows your FuBar addons in your LDB display.

RainbowEnchants

A simple addon that warns you if your pet isn't attacking while you're in combat.

Shows a window displaying any raid member below 10,000 health during the Chimaeron encounter.

Reverse Engineering will drill down and search your tradeskills for their elements

Adds a highlight border to items in your MogIt Wishlist, making them easier to see.

AutoFIR

Protractor

EyeCandy

Eliminates the spam from the chatframe and sums it up in a broker plugin.