The best item that dropped for me so far (that I noticed) was a blue (magic quality) off-hand source, which had only +damage and +intelligence, but the +damage was very high; something like 89-359.
It sold for 10 million gold.
It's easy to miss things like that, and vendor them along with all the crap.
One of my major qualms with the game is how difficult it is to spot good items.