I keep a tub of Baby Wipes, Cleaning Up by my overhead projector to clean my transparencies. The transparencies dry quickly and are ready for me to reuse for the next class. I allow students to demonstrate at the overhead quite frequently, and if an error is made, the Baby Wipes, Cleaning Up allow a student to wipe off just a small portion of what had been marked and then correct the error. Also, to avoid the nuisance of writing numerous hall passes, I have pre-written laminated passes that I store near my overhead projector. The students fill them out with an overhead marker, and when they return, they use a baby wipe to clean them for the next group of students.