It can get overwhelming when you have multiple students from different classes out sick, in band, or on a trip. To help keep track of who misses what I use a colorful hanging file folder set.
Each of my 4 math classes (plus my homeroom) has a designated folder. Anytime a student misses math class, they know that they must check their class' absent folder for any handouts or information that they missed. I also put any missed tests or quizzes in the folder as a reminder to both the student and myself that they need to make it up. (For tests and quizzes, I also keep a running list on my whiteboard of anyone who missed any.)
In the bottom folder I keep blank missed assignment sheets. Whenever a student in my homeroom is absent, another student fills in the assignment sheet for them so they know exactly what they missed. I've been using this system for 5 years now and really like it!