Visual Schedules are very important in classrooms for students with cognitive disabilities. All classes for students with MOID/SID/ are expected to have and use visual schedules. This paper created by Stefani Olson, Oklahoma Assistive Technology Center, gives very good explanation and provides many examples of workable visual schedules
Here is another helpful explanation with examples of successfully utilizing visual schedules: Download Set bc visual schedules
Some other web resources on visual schedules:
www.child-autism-parent-cafe.com/visual-schedules.html
http://www.dotolearn.com/picturecards/howtouse/schedule.htm
Video of various types of visual schedules:
http://video.google.com/videoplay?docid=5853947113791433682