A simple, quick tool this week, a stopwatch. An Online Stopwatch.
During most of my classes, I have the digital projector on almost all the time. Most of the time it is just showing a soothing screen saver, but it is ready to jump to life at any moment.
Pacing your class is important to keep the students active. Like exercise, you get the most gain when you vary the pace. Sometimes slow and careful, other times as quick as possible.
To encourage measurement of time, or even speed for fluency practice, we use timed activities. The easiest, simplest timing device I have found (and I have used more than a dozen) is the Online Stopwatch. Everyone in small groups can see the march of time.
With just a couple of simple settings, it is quick and easy to use, and available to any computer connected to the Internet. Here it is set to count down from 2 minutes. You can also use it as a timer. I display it full screen. You can use it with sound, but I find the buzzer at the end annoying.