This is a compilation of Addons made by various people. All acknowledgements for the individual Addons go to their respective authors.
In addition to the listed addons, I would also recommend Lightheaded, available from WoWInterface. This pack contains addons that can help you complete that elusive Loremaster achievement. Everquest and Loremaster give you a list of quests to complete, Lightheaded tells you where to pick them up and, with QuestHelper and TomTom, tells you where to go to complete them.