I had a hard time picking something out for complete strangers, but ended up settling for a strawberry pound cake. It didn't require refrigeration, and was likely to remain fresh for longer than something like a cookie assortment. In a perfect world, I'd have baked them something, but since plenty of people would hesitate to eat something prepared by a stranger (I might) I felt like a sealed bakery offering would be better for a first introduction.
The neighbors turned out to be a thoroughly lovely young couple named Bruce and Mary Catherine! They seemed genuinely touched that I stopped by to welcome them and were very friendly. Although they invited me in, I could see that they were still trying to get unpacked, so after a brief chat on the front porch I excused myself and left them to it. I couldn't be much more pleased. They're very young, have nice manners, and seem happy with their new house.
I hope they feel welcomed to the neighborhood, and I hope they liked the cake!