[Jerhal]

I usually drop quest stuff in the Adventurers Mart. Keys, scrolls, stakes, holy symbols. They always seem to be there when I come back. I havn't left anything important though. Also if you get a keep you can leave stuff there to pick up later.

If you do leave stuff for later pick up, keep in mind some places you can't get back to later once you complete the area. Like the Asylum, and Nalia's keep if you are not a fighter.