Goo.gl is Google's free URL shortening service. As I explain in the video embedded below, Goo.gl can be a good tool to help you get all of your students on the same webpage at the same time. By shortening a long URL to something manageable, you should be able to get all of your students on the same page more quickly than if you just wrote out a long URL on your whiteboard. Goo.gl also lets you create a QR code for any web link. Print or project that QR code and let your students scan it to get to the webpage you want them to see. Finally, Goo.gl includes an analytics feature that will show you how many times your shortened URL has been used.
See Goo.gl in action in the video embedded below.