1. WoW Matrix - This can be used to Update and find new addons with the push of a button. Never search for another addon again.
2. Quest Helper - Shows the location of the quest to be completed and where to turn it in, also it shows the quickest way to get to that location. Also tracks other members of your party's quest.
3. Auctioneer - Scan the auction house a few times to get the price averages (Recomend use with a mass auction addon) and it automaticly fills in the recomended price when you post it on the AH.
4. Enchantrix - Says the probability of what and how many of said item will be disenchanted from any item. As well as the value of the disenchanted materials.
5. Gatherer - Shows the location of Mining nodes, Herbalism locations, as well as chests, quest items, etc that you have found before. Very usefull in mineing.
WoW Matrix is located at
http://www.wowmatrix.com Just download it then use it to get the other addons =)