One of our sweet potatoes hung out too long in our bowl of spuds and onions that always sits on the kitchen counter and sprouted. The little leaves were so small and perfect, like little purple hearts, and so I decided to set it in a bowl of water and watch it grow. Grow it has. We now have a full-blown plant that threatens to take over the kitchen.
My mom said her grandmother used to sprout sweet potatoes and always had one hanging in her house. It's nice to know our little horticultural project ties us to our past.
Photo above from The Great Plant Escape which has a nice little "how to" description for kids.