Part of math class should be about the rigorous and beautiful categorizing of things. For this type of work I really like the blog @ Runde's Room. Pride in craftsmanship permeates her work and that is going to turn on some students a lot. We always want to make tough problem solving the focus of math class, but there is definitely room for these beautiful systematic reflections.
Keep a Binder or Tub ready with all of your sub materials. Items could include emergency fire drill list, dismissal list, phone numbers of important people in the school, how to use the phone, computer log-in, important notes about students. Then all you have to do is add in your sub plans for the specific day you're out. Also, keep emergency sub plans in the back just in case you are unexpectedly out. If you use a tub, you can also place the materials needed for the lesson inside.