WowAce

NRT_EPGP

This will keep track of how much you have paid per item in your inventory. Only one of (Auctionator, Auctioneer, AuctionLite,...

Test whether the player can really dispell a buff or debuff, given its talents.

Adds aura indicators to unit frames

Embeddable chat throttling library with traffic shaping and priorities

Makes those pesky garrison animations go away.

FuBar_NinjutFu

Helps you decide which ability to use next according to priority you set

Show coordinates on minimap

PetBar

FuBar_RLAssistFu

FuBar_SoulJarFu

NabuFiveSec

Shows your FuBar addons in your LDB display.

Considers an item against all the items you have to determine whether or not it is an upgrade

On login, displays changes to your guild since the last time you logged in.

Generate a macro with random mounts

GetInLine

Gives a Smoother Quest Experience

Fires events whenever a raid member "fails".