You know that site you use every day to learn about quests and where things drop? All of that data -- who drops what, the percentages, the map locations -- comes from players who take the time to collect it and contribute. The more people who contribute, the more accurate the data. These lightweight addons collect the pertinent information in the background and upload when you exit the game.
- The Wowhead Client will let you collect data for Wowhead and upload it at your convenience
- The WoWDB Profiler addon works in conjunction with the Curse Client to contribute to WoWDB