I try my best to avoid being absent from the classroom, but with IEPs and life itself substitute plans are bound to occur. I typically have all three grade levels read their novels with questions correlating to their chapter. This by far is the easiest plan for a sub to follow when I am absent for the day.
For IEPs when I am at school, but just not in my classroom I tend to continue what each grade level is learning. These plans are more involved and may include pictures and samples of what students will be completing. With every sub plan I create a Power Point that can be used for every class to help the sub and students understand what needs to be completed.