Crypt of Nadox is by far the best place I have found to farm these little bastards. The zombies all congregate by the docks and the nearby rooms/caves. In one clearing, I got 51 skins.
Zombie Skin Sells for 0 plat 0 gold 9 silver 0 copper at vendor Sateal Deirosap in the bazaar (human Monk level 2 charisma 141). I sell in the bazaar for 4 plat...
Pottery combines for Poison Vial (Triv. 148), Lined Poison Vial (Triv. 168), Sealed Poison Vial (Triv. 188), and Advanced Poison Vial (Triv. 196) all need one of a few old world skins. I have found that quite a few listed on EQ Traders as being acceptable will, in fact, not work. Zombie skins are your best bet for making poison vials and Unrest, from my experience is the best place to harvest them. Many tormented dead roam around outside the mansion and the drop rate of zombie skins from them is good. If you are waiting on them to repop, head inside the mansion to harvest poison ingredients such as Darkbone Marrow. I might add that tormented dead also drop Grave Mold and Amanita Phalloides. (Both used in at least two poison recipes.)
While hunting in a group in Unrest we received a shout that someone was paying for a stack of these skins. We as a group were able to put a full stack together and he paid us 300pp for the whole stack
They are used in making poison vials and some other items. It's a fairly simple combine in the 100's pottery skill range. www.eqtraders.com is a good source for trade skill info. Since my original post there are a lot of other ways to raise your pottery skill though.
Edited, Sat May 17 20:34:38 2003
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Voidslayer Jhereg, Destroyer of Worlds, Monk, <Celestial Navigators>, Drinal server Vanidor Silverbranch, Wizard, <Celestial Navigators>, Drinal server
While hunting in Unrest, someone started auctioning for zombie skins, I received 2pp each for them on the Seventh Hammer server, and he said they were used in pottery to make vials.