I know it's not a unique idea, but I just picked up a new mannequin head (shiny eyes to reflect lights nicely, life-sized, etc) off ebay through bensmannequin.com for about $25, and it's been a real nice help in working with lighting/shadows. They don't get annoyed after sitting for 3 minutes like my wife/kids do when I'm trying to practice various lighting arrangements.
This fellow sells a nice assortment (you can even pick up quite a shapely young lady if you're hurting for a date!).