Mac: Mountain Lion's new "Do Not Disturb" feature for Notification Center is lets you shut down notifications for a specified amount of time, but you can't set it to a schedule. Apple blog TUAW shows how to use Automator to tie Do Not Disturb to your calendar.
The process involves setting up a simple Applescript with Automator, and then tying that to a Calendar alarm. From there, you simple set up your Calendar with the time you want "Do Not Disturb to start running. Since it's linked to your calendar, you can set Do Not Disturb to automatically turn on every time you are in class, have a meeting, or when you just need to get work done. Head over to TUAW for all the code you need and a full guide.