1) Seedlings. The term dampening off covers a range of diseases and that attack a seed/seedling either before or after germination and cause the seedling to die. They can be caused by several different fungus and soil conditions. A few years back I read that if you dust the soil with cinnamon it will prevent dampening off. I've been doing it since with great results! (this also get's rid of those little gnats that somehow appear around seedling trays)
2) Wild mushrooms. Nothing worse then having to waste a beautiful day pulling mushrooms from the mulch in my flower beds. Mushrooms are fungus though, and by dusting cinnamon all over the mulch it helps to control mushroom growth.
3) Rooting hormone. Much cheaper then the chemical stuff they sell in the big box store and just as effective! Just apply cinnamon powder to the stem when you plant the cutting.
4) Ant deterrent. Ants do not like cinnamon! Sprinkle it in your greenhouse or around your garden beds. It will not kill the ants, but they will stay away from it. Sprinkle it by your doors if ants are coming into your house. They really hate to cross a line of cinnamon!
5) Plant wounds. Overzealous pruning or a slip of the weed whacker and you'll have a plant with a wound that needs fixed up. Simply dust cinnamon on the wound to encourage healing and prevent fungal infection at the same time.
6) House plants. Cinnamon get's rid of molds and mildew in house plants too. Simply sprinkle a bit of cinnamon on the soil. It will also get rid of gnats if you happen to have them buzzing around your house plants. These are the same gnats seedlings get, the cinnamon destroys the fungus they feed on and they will die.
Cinnamon also has some amazing health benefits