Check the wiki for an article on clutter. By the way, the 't' key is very useful for managing such clutter. (Shows you all the contents of a building, including what it is made from, as well as the contents of your wagon{s})
Basically, you need to watch out for clutter in butcher's workshops and any shops that see a LOT of use. Butcher shops pile bones and such up and aren't the highest of priorities for most dwarves to clean. Also, I'm relatively certain that any food, even if it's in a barrel, can rot if not put into a stockpile.
EDIT: Torak - generally, using an exasperated tone (swearwords and the like) and making comments to the effect that someone is without sense is regarded as demeaning and rude. I strongly recommend that you examine your choice of words in the future if you don't want to come across as an idiot of the highest degree. That being said, I think most reasonable people among us should be able to agree that from time to time mistakes in reading and typing can occur, especially when one becomes comfortable and "loose" in one's assumptions.
However, many people (especially in the day and age where using proper and reasoned grammar and vocabulary is considered "weird" and "gay") may still fail to grasp the concept of courtesy and thus try to make themselves feel superior by "flaming" you. I plead with such people not to harass you about this any further, as doing so would only exacerbate the situation.
SIDE NOTE: Dear Diary, today I finally got to use the word "exacerbate" in a sentence. Now my life is complete. Or at least as complete as it can be without a final, perfect release of Dwarf Fortress.
EDIT: Good cripes, if I don't stop editing this I'll never get to sleep. (This is at least the fifth time, I just keep deleting the little edit log.)
[ December 12, 2007: Message edited by: Reasonableman ]