Here's an update....
The neighbors across the street are NOT his owners.
Nobody in our neighborhood knows where this little dog came from. Our next-door neighbors (the ones whose family raises working border collies) think that he's a catahoula mix. I personally am thinking that perhaps he has some Australian cattle dog in him.
He's staying in the yard for now. He has plenty of food, water, and a doghouse. I'm going to put an ad in the paper tomorrow. I'm just going to say "Found medium sized male dog in ____ area. Call to describe."
Hubby is already making plans to keep him. "Well, we already have a crate and stuff. Our house isn't that big, but he's a just little boy too. And of course we'll have to get him neutered "
So, yeah. It looks like if we can't find his owner, we're probably going to keep him. But I'm still resisting making permanent plans! I want to be sure that his owners aren't out looking for him; I'd feel terrible taking someone else's dog.
EDIT: Drat! Fate is interfering again! About 8 months ago, I ordered a custom-made 2-inch wide leather collar for Zeus. However, it didn't look quite right on his long neck. We just put it on the pup, and it looks magnificent!