My Holy Grail for a long time has been a treasure item generator that would come up with every thing you might think of and some you would never think of. I pondered this a little before and decided there are so many variables, it's probably best to separate out what the item is from the qualities of it. So here is a roll all the dice chart to generate the qualities for any object.
Let's say the party finds a cup
1, 6, 1, 6, 10, 9
This cup is crude, half-size, 600 years old, and in pristine condition. It is made of copper and is notable because it is an important ceremonial item.
Or a key
3, 2, 8, 2, 9, 20
This key is well-made, twice normal size, 200 years old, and has been repaired. It is made of crystal and is notable because it is from some strange race or culture.
A note on notability-- with this chart pretty much everything will be. You could ignore it if you just want an run of the mill item. Also, that is the one aspect that most likely won't be apparent from the PCs just examining the object-- you could at least guess on most of the others.
A note on value. These characteristics should probably affect the items monetary value. But the variables depend so much on context I've left that out. For example, an old sword might be more valuable because it is an interesting artifact or it may be worth less because it is not made with the most current technology. Likewise, an object that is supposedly cursed (think the Hope Diamond) might be spurned or it might be sought out by a particular type of collector. I'm not happy to leave more work for the DM but I'm not sure how to do this otherwise.
Ideas for additions or revisions?
Update 6/20: I've fixed the kooky "Size" math. I would rather it be in words-- half-size, double-size, etc-- but got tired of fighting the formatting (maybe next revision). I also removed mother-of-pearl from materials (consider it a possibility under "Gem") so I could put a "Roll Twice" result. Because some cups should be gold-washed, or filigreed, or set with gems.