I've used various resources to teach vocabulary over the years such as Vocabulary from Classical Roots (noting the Greek and Latin morphologies of the English language) and Wordly Wise 3000. I've made up my own weekly assignments, sometimes letting each student pick a word from the free 5000 word SAT vocabulary list.
Lately, I've been making use of Vocabulary.com which provides pre-made lists using words from current news articles in their "This Week In Vocabulary" collections (though they also have any number of other collections ranging from World Series baseball terms to helpful poetry terms.
The website offers (for a small fee) the ability to educators of providing practice, quizzes and spelling bees for the students. While the grade-recording is a bit cumbersome, it can still help free up some time for other things a teacher must prepare and supervise.
However, as I learn the website, I found an even more impressive tool within. I've often wanted to teach vocabulary based on the literature I am having the class to read.I believe that reading literature is one of the best ways to grow a vocabulary - if one bothers to keep a dictionary close at hand while reading.
I have, in the past, slogged through chapters, underlining every word which I thought might be unintelligible to students and typed my own vocabulary lists and exercises. Very time-consuming.
But then I find that one can cut-and-paste an entire chapter into the "Create a New List" Vocabulary.com feature . . . and the site automatically creates the list for me! Marvelous! This will be especially helpful as we take up the novel Frankenstein once more. Give it a try with anything from The Scarlet Letter to Paul's first letter to the Corinthians.