I use them for assignments that I need to check. My children use them to keep pages of a story together as they are working. I use them to hang work on the lines above the bulletin board. They can be painted to match anywhere in your room or labeled quite easily with permanent markers for math, spelling, science, etc. I don't know about you, but I receive many memos a day.
Memos can tend to get thrown away or lost very easily.
I keep all the memos in it and refer back to them as necessary. On the first day of class, I hand every student an index card. I collect the cards, place them in my podium, and use them to randomly call on students. When I send notices home or make contacts with parents or students, I place the date I sent it on the index card. At the end of the year, I pull the cards out when students call off their book numbers.