WowAce

Creates a broker plugin for all your broker launchers

Adds tier set number and difficulty indicators to tier item tooltips.

Calculates the relative value of attributes towards physical dps.

Ratings

Shows what stat was reforged in item tooltips.

Shows loot information in item tooltips

Tooltip text modiffier based on DogTag.

Enables RatingBuster to calculate selected buff effects even if you don't really have them

A set of datatexts for ElvUI that provide you with detailed info about your professions

Very very simple tooltip

Shows the source of an item as a tooltip

LibDataBroker plugin showing some random XP related data

Adds information about the items tokens can purchase and vendor location to tooltip

Provides info about spell teaching items.

A standalone addon to walk around the 4.0.1 inspecting BUG. Also provides help for other addon that need Inspecting

Really very early stage. No, earlier than that.

LibQTipClick-1.0

Shift-clicking on a user name in chat shows a tooltip with their whois information.

Adds tooltip for debuffs (and other things? you found out: no).

Show all characters' currency in the currency tooltip