This isn't so much a ghost story, more a doppelganger story but it sort of counts.
I had a school friend Vicky who was always chronically late. When I got home from school that day, my mum said, 'Oh I saw your mate Vicky walking along after I dropped you off.'
'Yeah she is always late,' I replied. My mum described the clothes Vicky was wearing - school uniform, with a white scarf and an inappropriately short skirt for winter, with bare legs, red from the cold (she is Scottish and we used to joke she feels the cold less than us soft southerners!) I was just about to say 'but she was wearing trousers today,' when my mum stopped me. She said 'and then I drove on, and on a different road further along, saw Vicky again, walking with her brother.'
My mum was so confused, she had to pull over and make sure she was seeing what she was seeing (she didn't drive back to see if she could spot the first Vicky). The 'real' one was wearing trousers. I would normally dismiss this as mistaken identity if it wasn't for the fact my mum is really good at recognizing people and Vicky with her red, frozen legs and tiny skirt is hard to mistake. She's facially quite distinctive looking too, with very thick eyebrows, a weirdly cut fringe at the time, unusually crooked teeth, turned up nose, tall and very pale. One theory I have is that she could have been anxious about being late for school and astrally projected herself further along in her journey. My mum was so freaked out over this, she couldn't stop thinking about it! It just seems weird that there would be two people who were both in the school uniform, both late, who both looked like Vicky. There was no one else in the school who looked like her.
It's not the first doppelganger story I have - I wrote one about a friend a few years ago. It seems a lot of people on this site have had experiences like this, so that was my contribution!