Dog hide can be found on dead dogs in Fallout: New Vegas. It is weightless and can be sold for caps.
This item can also be turned into a Leather belt (Dog hide belt) at a workbench if you have a Survival skill of 5 and have the Honest Hearts add-on. This slightly increases its value from 4 to 8 caps. The resulting belts can be used for crafting super stimpaks and weapon binding rituals.
Although it can be found on most dogs, some dogs won't have it in their inventory.