What's the difference, really, between shuffling off to the Xerox machine to make 50 copies of the TPS reports, and shuffling down to Un'Goro Crater to get 15 pieces of dinosaur meat for your Venomhide Ravasaur? Not much, except there's a more tangible reward for the latter. Gamer-friendly PIM QuestTracker (free/donationware) manages them both the same way.
If you're looking for something to replace Microsoft Project, this isn't it. Featurewise, QuestTracker is very sparse, on par with the task lister built into Gmail. It supports one level of hierarchy; you have quest groups, and quests within them. You cannot reorder quests in a group, or groups in the window. Quests are either done or undone. Each quest can have a detailed text description, describing what needs to be done, how, why, or anything else.
You can set a quest to be recurring. For example, no matter how often you complete the quest "Empty The Trash," it comes back each morning (or whatever period of time you set), and you don't even need to hunt down a goblin with punctuation hovering over his head. By default, completed quests are hidden, though not deleted. You can show completed quests, but instead of being checked, they are highlighted in green.
It is also possible to export or import quest lists, which is useful when upgrading to new versions, as QuestTracker is rapidly adding features. This is important, as QuestTracker right now is a nifty idea waiting to blossom. Simply calling tasks "quests" isn't an exceptional bit of functionality. I would love it if QuestTracker borrowed a bit more from Warcraft. For example, a typical WoW quest would have you gather 15 goblin ears, and track that you've collected 7/15. This is more useful than a simple "You have done it/You have not done it" interface. Many quests are also staged: Do part 1, you get part 2. A tracking system which didn't show you the "next quest" until you've completed the "current" one would be helpful, adding more depth and imposing an order on completion.
QuestTracker would also benefit from an aesthetic makeover. It borrows concepts from WoW, but is very graphically plain. The overall structure--"Quests" to the left, descriptions to the right--is the same, but no one looking at it would confuse it with an in-game window. There are tons of fonts out there which strongly resemble Blizzard's chosen typefaces; you might as well play up the connection in look and feel.
If you need a very straightforward quest...I mean, task...tracking program that is extremely lightweight (ideal for netbooks), QuestTracker is worth checking out. Despite being a fairly early beta, I noticed no stability problems. Development is ongoing, and QuestTracker is free and open source. Overall, I'd say Quest Tracker shows promise for open world task management quests, but it isn't ready to start seriously raiding endgame productivity instances.