Just for what it's worth, all spiders are poisonous. There's no such thing as a non-venomous spider so far as I know. It's just a matter of whether the spider's fangs are large enough to pierce human skin and whether the venom is potent enough to really do anything to humans.
It just so happens that the only two species of spider in this part of the country that do any more damage than an insect bite are the Brown Recluse and the Widow Spider (sometimes black, sometimes brown) as an above poster mentioned.
That being said, if a Wolf Spider jumped on me at any point, I'd probably lose my ****.