I think snakeskin would also be a good candidate for a weight reduction effect. As someone mentioned upthread (or maybe in a different thread -- can't find it right now) prepared snakeskin is a remarkably tough leather, but it's also very light weight for that toughness.
A bonus vs. poison might be more appropriate on one of the more fanciful creature types. Maybe a gargoyle or hook horror hide, or a sword spider or Ghakis spider carapace.
Speaking of Ghakis, there are yetis up there, right? How about a yeti hide giving a stronger cold DR than what you get from other hides? (Though skinning and wearing something that human-like might be a bit much for some people. Me included, now that I think about it.)
Supposedly ostrich leather is really strong and supple. Maybe some sort of large bird could drop a hide that gives a move silently bonus. (I tend to ignore birds unless I'm really desperate to tame an animal, so I don't know what's out there and larger/rarer than vista chiri and ravens.)
A few times I've seen a non-tannable tiger hide item at Murnu's. This could be added to the leatherworking menu with a bonus to influence (because tiger is just so neat looking
It's a shame we don't have any acquatic monsters. Ray and sharkskin would be good candidates for a partial AC bonus (pierce/slash, maybe) with a move silently penalty. Eelskin could give DR vs. electricity. (Yes, I know eelskin isn't actually made from electric eels, but it'd be too perfect to pass up.)
On the woodworking front, I really like the idea of bodak and vampire teeth giving bonuses when used as arrowheads. How about doing something similar for the large bones dropped by some undead? They could be used as arrow shafts, and give a +1 damage bonus vs. humaniods and animals, -1 damage penalty vs./ undead. Or instead they could be an "antler" for use in composite bows, giving an attack bonus vs. humanoids and animals and an attack penalty vs. undead.