Severus Snape is about 12 inches tall and knitted from acrylic yarn. He is dressed in his trademark Victorian frock coat complete with tiny buttons and is delightfully grumpy.
He is hand-knitted from one of my own patterns and is looking forward to sitting in your house and taking house points away from you at every opportunity.
Update Nov 2010: Severus has gone off to a new home, but check
my Etsy shop to see if I have another for sale, or contact me if you'd like to commission a Snape doll.