A few nights ago when I came home from work at about 11pm., my six month old malinois was out in his kennel barking. My wife said he had been barking for about 1/2 hour non stop. So I let him out of his kennel and just hung out with him in the back yard for about ten minutes and then put him back. Five minutes later he started barking again. Normally I would let him bark, but because of the time of night, I didn't want to upset any neighbors so I brought him in the house. That's when I noticed that his right side of his head was very swollen and his eye was almost swollen shut. The swelling started just behind the eye and continued out to his nose with his upper lips on both sides being very swollen also. I didn't notice this the first time because I didn't turn the outside lights on. The first thing I thought of was a snake bite, but we don't have much of a snake problem here and I checked the kennel and could find nothing. There was also no sign of a bite. He didn't seem to be bothered by it. Just slightly aggitated. He still wanted to play tug and could grip fine. I kept him in the house for the night and by morning, the swelling was almost gone and by the afternoon it was totally gone. The next night, the same thing, only the other side of his head and the swelling wasn't as bad. So, I sprayed the kennel and shed that it's attached to with Tide thinking it was a spider. I haven't seen any new webs but those daddy long leg spiders are still around.

Anyone have any experience with dogs and spider bites? Does this sound like it could have been a spider?

The only poisonous spiders in the US are the Brown Recluse and the Black Widow. The Black Widow is the only one in your area but that doesn't sound like a Widow bite. Are there any wasp/hornet nests around? That's more the reaction your describing.
Daddy Lonleg's mouth parts aren't powerful enough and to small to break human or dog skin.

No bees, hornets, or wasps. I checked for nests.

Velvet ants are wingless wasps. They don't make nests, and they are solitary, and they pack a heck of a punch, sting-wise. They're called "Ox Killer" because their sting is so strong and painful. They look like a great, big, oversized, furry ant, with black fur everywhere except their abdomen. The abdomen is bright red. We have them in Missouri, don't know about PA, but if you have them out there, it's possible he got to aggravating a velvet.
I like to had heart failure when I found my female minpin playing with one on three different occasions last year. She was pawing it and she's quick, but thank goodness I killed it before it had a chance to connect with her.

One of the people in the club lost a dog to a spider bite. It quickly became infected and killed the dog.

No velvet ants around here. At least I never heard of them.

They are actually a kind of wasp. More about them here.