I used all sorts of extracts (lemon, peppermint, etc) when I made playdoh for my kids. They had as much fun making it as playing with it.
I had to laugh at how young some of you are. When I was little, we didn't have really fancy playdoh things. Those didn't come out until mid 70's. I used cookie cutters and kid scissors on mine. There was one squishie thing available and it looked kind of like a large garlic press with a slider that had like 4 different shapes to be extruded from it.
Thanks for the trip down memory lane. I still like to play with playdoh even if I don't have any "kid units" around.