Another little classroom hack I've stumbled across recently:
Sometimes you just need a set amount of time for an activity. Maybe you're practicing timed tests. Maybe you need to make sure you get finished with your class discussion at a set moment to have time for something else. You could just tell a student to keep an eye out on the clock for you (that usually works pretty well). You could try and keep track yourself (but if you are like me, you often get sidetracked and forget the time).
Never fear, the Internet never lets us down.
An easy and fairly discrete one is on Google. Just type in TIMER into the search bar to get an adjustable timer. It has a rather annoying beep until you turn it off. The pros - it's quick and not distracting.
You could also try these classroom timers: http://www.online-stopwatch.com/classroom-timers/ They are much more fun, but also distracting as all get out. I imagine my eyes as a student would be constantly on them. However, if you are doing a long group activity where students are being loud anyway, this might actually help keep them on track. If nothing else, pick the snail race and let students bet grade points* on which snail wins.
If you have any good timers or time keeping system, don't be stingy! Share in the comments.
*Facetious is the only word in the English language with all five vowels in alphabetical order. Facetiously includes the sometimes y. It is also what I am being when I say "bet grade points", no matter how much fun that would be.