Liberty University created a Firefox add-on that counts the number of words in discussion board, blog, journal, and wiki posts made by students. This add-on lets faculty quickly see the number of words a student has posted to make grading easier.
To get the add-on, go to https://addons.mozilla.org/en-US/firefox/addon/Word-Counter-Bb/ using Firefox. Click the green "Add to Firefox" button to install it.
After installing the add-on you'll see something like this in your Discussion board threads.