WowAce

Reno is a slash-command that can patch predefined options in a macro to change which abilities will be chosen.

A Mount and Companion manager

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

Helps you automate selling stuff.

Adds achievement reminders to BigWigs

Disease Tracker for Death Knights.

Objective Tracker

Proximo

Automagical macros for each talent tier.

Gives a score for your kit allowing easy comparison with others, also colour codes kit based on appropriateness for your level.

First Aid data for Ackis Recipe List.

Customizing your buff display

RaidSpy

Simple display and management of Away / AFK / Busy / DND status via broker or minimap

Configuration for LibToast notifications.

Assister

pDebuffList

OneChoice tries to help you reduce quest reward choices down to, ideally, one choice.

Shows current/dot cast haste values

Enables user defined sounds for Party, Guild, Raid and Custom Channel chat messages.