There are only a couple of really troublesome spiders in Pennsylvania. Perhaps the scariest of them all is the brown recluse spider. In addition to neurotoxic effects that can cause nausea, fever, chills, as well as other symptoms, the brown recluse's bite will also cause the tissue around the bite to grow gangrenous and die. This entire process, I have heard, is extraordinarily painful. Luckily for Pennsylvanians, there are few of these dangerous spiders around, and your most likely shot of running into one is if it makes a home in a box and gets shipped here.
The other scary spider is of course the black widow, that sexy arachnid with the black carapace and red hourglass on its belly. The good news is, when it first bites you, it won't hurt all that much. The bad news is that its venom is highly neurotoxic and will make you very sick. The bite of the black widow has been known to kill, but usually only infants and the elderly.
Beyond those guys, Pennsylvania is pretty safe. The worst you can expect out of a spider bite is a little pain, maybe a little nausea. I was a bit scared last night when I got bit by some little brown spider, but I survived, and I am stronger for the experience. I think its my first spider bite -- it felt like a bee sting. It was wierd too, as my hand was bitten when I swatted it, even though it was crawling on my leg.