I have been wondering about this too. I have been using a Henna shampoo and it leaves a scent on my hair- I am not sure if I like it or not but other people have commented on liking the smell.
I also have been known to put a little of my purfume on my hands and smooth through my hair but I know that is not the best thing.
I do use a lavender EO and water in a mister bottle. That leaves a nice smell but its not noticeable really!