SpellingCity simply put is the best site around for all Vocabulary and Spelling needs. It even has an educational portal that allows for student tracking and educators to add assignments/word lists to their students. Also, there is a free mobile (iOS, Android, Kindle) that interacts w/ the web portal to allow mobile learning for students. SC also has a wide variety of resources and videos, but allows teachers to create their own customized word lists and integrate them into educational games for their students.
Here's an example... "Homonyms, homophones and homographs can bring confusion to even adults and teachers! VocabularySpellingCity can help anyone master these word groups. For clarity, we've brought them all together on one page. It makes it easier to learn the difference among the three types of words using the definitions and homonyms, homophones and homographs examples below."
I highly recommend checking out SpellingCity by clicking here!!!
*SpellingCity is an advertiser of Technology Tidbits.