Twenty years ago I worked in a small agri-business in Salinas CA. The greenhouses and office were the first buildings on that site; no other structure had existed prior to its construction. The area had been mainly fields and ranch prior to the business being there.
The location was very close to Old Stage Rd, which has a well deserved reputation of being haunted. One of the most famous stories is the headless woman who was murdered along the road, who has been reported to have been seen walking along the side of Old Stage with her head in her arms. I frequently saw odd lights during the winter commute home that looked like on coming headlights and then would disappear when you drove towards then.
The haunting started rather subtly; in fact we thought one of the admin people was pranking the rest of the office staff. Office supplies would be moved to odd places at night or mysteriously disappeared to be found in the middle of the office floor days later. The TV in the conference room would switch on at odd times during the day. As time went on, the incidents became more pronounced. People in the office and work crew began to catch fleeting glimpses of a dark haired woman in a white shirt. She bore a passing resemblance to one of the managers to the point where people would catch a glimpse of the ghost and think the manager was actually in the office sitting at desk. I would be working in the front office and hear someone call me from the back, only to walk over and find no one was there.
As time went by, most of us in the office became used to "La Fantasma". We went through a few receptionists during this period and each time someone new started, our ghost became very active as though she was either upset by the change or testing out the "new kid". One time, our poor cleaning person was cleaning up in the lab in the evening. As she worked, she was listening to the radio. All of a sudden, the radio switched stations (from one end of the dial to another) and went very loud and all the lights in the lab went out. The woman refused to work the night shift after that incident.
Along with hearing her call my name and the occasional glimpse of her at a desk, two incidents stand out for me. I was once working late to finish a programming project, so I was the last one out of the office that night. I carefully went through the offices, locked up the inner office doors and shut the lights out. I locked the main door and headed towards my car. All of a sudden all of the lights in the office went back on. While I thought it was funny, I didn't have enough nerve to go back in the building and shut off the lights!
Another time, I went into the computer room first thing in the morning and found that the door was blocked. There was only one door in and out of the room and somehow the garbage can (which was full of green bar computer paper and heavy) had been pushed against the door, which swung into the room rather than out. She never seemed to be malicious, but rather playful in her activities.
The only other haunting at the facility seemed a bit more dark and foreboding. Across from the main office there was a field that came off the main parking lot. On several occasions, some of us saw a tall dark man in a wide brimmed hat that seemed to either pace the field or stand on the edge of the parking lot looking towards the building. He never seemed as substantial as the female ghost of our office, but seeing him gave most of us the willies.
I don't know if the haunting continued after I left the job over 10 years ago. But it was an interesting place to work nonetheless!