In my case, it sounded like something had crashed in the house. Immediately, I thought we were in the middle of another earthquake. However, I didn't notice any residual rocking. My second thought was that one of my children had fallen out of bed. As I didn't hear any crying or further movement, I then wondered if the cat had knocked something over in the art room. Remembering that the art room is locked up at night, I then decided that one of my Star Wars ships must have disconnected from the fishing line that keeps them hanging from the ceiling. Too tired to investigate, I went back to sleep.
Later, after letting the dogs out, I noticed how skittish they were and remembered that they get that way when they're afraid of snow falling from the roof. I realized that it was a falling snow pile that must have hit the ground on the side of our house near our bedroom. I eventually checked as I was leaving for work and confirmed that most of the snow had fallen at some point in the night.
When I mentioned my theory (before confirming it) to Janelle before leaving for work, she said that she thought it sounded more like gunshots when she woke up. It wasn't until this evening that we discovered we woke up for different events at different times. In her case, one of our neighbors was lighting fireworks for some reason. They did so again tonight.
I will say that these strange sounds made for some strange dreams.