It was brought to my attention that an online timer I had posted about previously was no longer online. That got me looking around for other online timers, and I have found several that serve some different purposes fantastically...
How often have you told your students, "You have 10 minutes to complete this activity.", only to lose track of time thereafter. Luckily, there are many online timers that make it quite simple to track your time. Even better is that many of them put a large display on your computer that you're students can see to monitor their time.
e.ggtimer.com - There's a couple of things I really like about this timer. First, you can actually type in the time you want to use for the timer in the url, for example, e.ggtimer.com/5minutes, would automatically pull up a website with a countdown from 5 minutes. You type in any time amount here, as well as a few other cool things that you learn about on the site's main page.
Online Stopwatch - This site can serve as a stopwatch or a timer. To use the stopwatch click the green arrow stopwatch link. You'll then be taken to a page that will allow you to start the stopwatch. If you need go back to the main page just click the provided "back" link. To use the timer function of the site, click the "Count Down" red arrow. Use the buttons on the screen to set your time, then click the "Set" button. From here you can start the timer.
timer.onlineclock.net/ - This is a simplistic timer that can be shown quite large on your screen. Just use the links in the upper-left to adjust the size. Use the drop-down menu under the timer to set a time. The timer will begin as soon as a time is selected.