A few folks over at the Twisted Nether Wiki have done a great thing and compiled a nice full list of all of those little online WoW utilities that we talk about every once in a while. From character improvement tools like Be Imba! to resources like Kaliban's Loot Lists and even humor sites like WoWBash, if it's online, WoW-related, and worth visiting more than once, it's on this list.
And of course it's a wiki, so even if it's not on that list, you can add it. But it is cool to have all of those resources in one place -- we mention them, obviously, when there are updates to share, but if you don't bookmark them when you hear about them, they might have fallen off your radar. There are so many great and well-designed tools out there for players to use that something like this, tracking them all, is great to have.