! Dubby, a bellringer is a small activity that students do as they are entering or exiting class. Usually it is used as a small assessment piece.
I suppose it depends on what you have covered in class already. I always use review topics from earlier in the year. You could always have a question on the board, then just have a stack of index cards or post it notes for them to put their answer on.
You didn't specify grade levels, but some ideas I have include:
How do you shut down the computer properly?
What key(s) do you use to type a question mark?
What is the proper spacing for an essay?
Give me the steps to change your font.
If you have your hands properly placed, what finger do you use to type the letter B?