chuck, i leave all my extra stuff in barrels next to the merchants.
this is not only great for storage, but quite nice when changing acts as i just pick up the 2 barrels and take them with until i find another suitable resting area. <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" />
i've also had the barrel (or duplicate) show up in a BF dungeon.
it doesn'tseem to make any difference to your items though (at least in my experience) as they'll ALSO be in the same barrel you have up top.
interestingly, when i've had this happen, it's actually worked out quite nice as i could deposit all the collected stuff from the dungeon in the dupe barrel and then just continue along with the exploring. when i get back to the merchants, the (new) stuff was there in the barrel. pretty sweet actually!
my guess is that there is a code number for those barrels, and when the number of the barrel you're using up top cycles through, it gets used in the dungeons - complete with whatever you've put into it.