I recently came across a web site and blog that provides hippotherapy information and activities. This is awesome sinc I couldn't find this when I started out 4 years ago and we therapists love resources. check out:
Horses can Help
and the following picture game used during a therapeutic riding lesson.
http://www.horsescanhelp.com/2010/03/09/therapeutic-riding-game/comment-page-1/#comment-31