I've had some fun at a new site called Vocabulary.com. Below is a description of the program from the developers:
Vocabulary.com is a new FREE site that’s focused on teaching vocabulary in a way that keeps kids engaged. Students don’t study at Vocabulary.com, they play The Challenge, a game that rewards vocabulary learning and effort. It’s also adaptive; the site offers more than 100,000 questions to teach more than 10,000 words, so it chooses words and questions based on how you perform over time. With The Challenge, if you miss a word, we keep working with you until you master it.
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