I asked permission from my friends before posting this, as it is their house. They're a married couple with two children. I mention this because the kids will come into play, and to give an idea of what type of people they are. For the duration, I'll call them Tod and Carla, the kids I'll refer to as Peter and Paul, none of which are their real names.
The first incident I know of, Tod mentioned that shortly after setting up the Christmas tree, he'd seen an elderly man shake it and then disappear. He said the man seemed genuinely curious what it was, and he got the feeling the shake was experimenting a little with it.
The next incident involved me directly. Carla had just left with Peter and Paul to take them to school, as they lived too close for a bus and too far to walk. Their leaving woke me up slightly, but I was able to move and everything, in fact I mumbled a "later" to Carla as she left. After they'd pulled out of the driveway, I heard the distinctive sound of a cat contently purring next to my head. At the time, they didn't own a cat, but it sounded happy so I wasn't scared. As I was listening to this, I also got a distinct feeling of a Native American man sitting in the middle of the floor, Indian style (I don't know any other way to describe that style of sitting). The man seemed to know I was there and in fact be there because I was there. Again, he didn't seem angry, more of a friend.
The next one again involved me, and happened in their basement. After my experience with the cat and the man, they told me that if anything showed up to tell it that they told me it had to leave. Well, I was creating a character because we were going to roleplay the next night after Tod got home, and being a Night Owl anyways, I decided to get a jump on mine. As I was doing so, I suddenly felt a pacing behind me. I told it what they told me to say, and then apologized as I disagreed with their verdict. In response, the book I'd just closed shook at me, slightly above where I'd sat it. I don't know if this is connected or coincidence, but we found out a truck driver had slid off a bridge around that time and died.
We now turn to the only hostile one I've experienced there. I was sleeping on the futon in the living room, and Paul, their oldest, was sleeping in the top bunk of his room with Peter in the bottom. At the same exact moment, or as near as humanly possible, Paul and I woke up from severe nightmares. It wasn't a matter of Paul's screaming for his Mommy that woke me, more like as I was waking up and convincing myself it was a dream Paul screamed. I turned and looked at the front window as there's a church there and I figured I'd focus on it to calm down. I think I saw instead what gave us the nightmares. There outside the window was the profile shadow of a hunched over figure.
I know this sounds like the old hag, but Carla confided in me about a week later that after that night, she had gotten up to go to the bathroom and happened to look into the living room. There in the middle of the room stood the same figure I'd seen before. She demanded it leave and never return and as far as I know it hasn't as of this writing.
Finally, when the family goes on vacations, I tend to watch their house for them. I've experienced odd little things like the kids' bedroom door not staying shut even when I tug hard on it to make sure it's latched. One time though will always stick out in an "Awww" and a sad sense at the same time. This is a while after the experience before with the cat purring, and since then, they'd gotten two cats, Molly (a pure black cat) and Hermes (a mixture of colors with tiger striping). One night while watching the house, I looked into the kitchen and thought I saw Hermes eating. I decided I was going to pet him so I called to him. He looked up at me and started walking towards me, so I went to meet him at the doorway between living room and kitchen. It wasn't Hermes, because, as it got nearer the door, I bent down to pick him up, and the cat leaped as if to leap into my arms playfully, and disappeared as his front legs left the kitchen.
Now, during all this, there was a house next door. While they've lived there, there was a period where people moved in and quickly moved out. The house was in disrepair, and we figured it was because of that. After a couple years, it became an abandoned house, and was eventually torn down by the city. Ever since it's been torn down, there have been no more odd occurrences. Can one house's ghosts "visit" the neighbors?