Word clouds are a staple of web pages on the internet these days, and there are a number of apps that will generate them for you. The one shown here is built from some of the most recent posts on this blog.
An easy way to generate word clouds is using Google Docs. In your Google Doc, go to Add Ons -> Get Add Ons, and do a search for Word Cloud Generator. Click on the Free icon, and it will be added to your Google account, and will be available from any device you use with Google.
Once it is installed, and you have some content in a Google Doc to put into your Word Cloud, just go to Add Ons -> Word Cloud Generator. Select Classic, or Modern. The latter is recommended. A window will pop up on the side, and you can choose Append Large or Append Small. There is also a Download icon. The Advanced option gives you different coloring choices.
You can have your students make word clouds of their writing assignments to make an otherwise dry homework assignment into something colorful and fun. It will let them see their word frequencies in a graphical way as well.