WowAce

InventoryLib

"Range finder/display for Discipline's Holy Nova"

Displays the zone level ranage of the zone you are in and also gives you a suggest zone and instances to be in.

Notifies you of experience gains

Combat log replacement

Adds the "pixel perfect" font "Silkscreen" to LibSharedMedia

NextStep

Lists and/or reminds people missing flasks or food buffs at every ready check.

Compact scrolling vendor frame

Keeps track of gold and cash flow across multiple characters

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

HazLoot

Out of Mana bar.

Sneakily inspect how much gold your mouseover target has made so far.

Light-weight enhanced casting bars

Checklist and notes addon.

Simple and rich Death Knight rune customizations

BigTrouble

Leveling guides for trade skill professions.

Client for MagicDKP which handles standby calls and bidding on items.