Here is a kit that I composed based on little activities or brain breaks that I have experienced. I made them up into cards for convenience. The general principle is that students' attention span is a minute/year of age. If that seems like too short a time, definitely change activities every 15 minutes or provide a brain break.
For the activity cards, click here.
For ease of access, I colour matted my cards according to approximate time needed. A purple card in my deck would take about 5 minutes of class time, whereas a pink card might take 5 seconds.