If you are looking for a run down on nearly every item, as well as information on World of Warcraft quest help, Thottbot is my favorite site, it is one that offers you a wealth of information.
It can be useful for completing quests, particularly for those players that tend to use an add-on with waypoints, or for the cases where the add-on does not work as you expect it to.
Thottbot can also be very useful if;

1. You want to find out where certain items have dropped.
   
2. You are looking up class-specific gear or spells.
   
3. Or even if you are looking at the different recipes that are available for your craft.
   

Nearly all players no matter what level they are at should be able to find something useful on this website.
The majority of players will get the maximum use out of the search feature.
Say, for instance, you pick up some "Mystery Meat" while out farming.
Simply search "Mystery Meat" and it will show you that it is needed for the cooking recipes;

• Carrion Surprise.
  
• Dragonbreath Chili.
  
• Or Mystery Stew.
  

It also tells you there is a vendor in Howling Fjord that sells it and what beasts drop it when killed (as well as an approximate drop rate).
You can then decide if it is worth it to your character to cook it, sell it, or vendor it.
If the item in question is needed for a quest or is a quest reward, you will be able to see this as well.
Another interesting feature of Thottbot is the ability of other players to have a running commentary about the item or quest.
As with any public forum, these comments can range from meaningless to actually quite useful.
Look for comments that are highlighted in yellow, these have been given a good rating by other readers or players, and they often contain special information for example;

• Where an item can be found.
  
• Tips for killing a particular mob.
  
• Coordinates.
  
• Or completing the quest.
  
• Plus plenty of other pretty useful information.