There are hundreds of spider types in The Wastes. They all tend to be hairy, colorful, and of moderate size (1-1.5" or 2-4 cms).
The most common spiders that people notice are called Waste Spiders. These spiders are larger than hand sized; being big, furry, and in a mottle of earth tones. These spiders do not spin webs (but do use web as drop lines), but have a scorpion-esk tails with potent paralyzing venom.
Prospectors of the right inclination will stalk Waste Spiders and "milk" them of their venom. This venom has a variety of therapeutic and less savory uses.
Note: some Waste Spiders have been reported to "spit" some kind of venom as well. But these may be rumors. However, thanks to the special nature of The Wastes and Hellpits, anything is possible.