WowAce

Raid level alternative player power warning (Atramedes, Cho'gall, Lord Rhyolith)

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

aUF_RangeCheck

DotDotDot

Aspect checker addon for Hunters.

Estimated time until current target will die.

BeneCast 10

ShadowGreenLight helps you decide if recasting SWP/Corruption is worthwhile

Tracks profession specific cooldowns and items across all your characters

Keeps track of space left in your bags.

Replacement for default bags.

NBuffBars

Lightweight time/date display with optional hourly chime.

KillingSpree

Allows the user to customize the the tooltip with lua-scripts

adds navigation buttons to Encounter Journal

Transcendence Monitor for Monks

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

Alternate Rune Display

Simple right click casting.